NOVELTY - Preparing 2-thia-spiro(3.3)hept-6-ylamine hydrochloride salt (I) comprises adding 7-phenyl-6,8-dioxa-spiro (3.5) nonane-2,2-dicarboxylic acid and pyridine according to a mass volume ratio (g/ml) of 1:5-15 in a reaction vessel to obtain a mixture, reflux heating the mixture for decarboxylation reaction, evaporating under reduced pressure to remove pyridine to obtain residue, adding hydrochloric acid into the residue to adjust pH value to 5-6.8, extracting the residue with a first organic solvent to obtain organic phase, and drying the organic phase.    USE - (I) is useful for synthesis of anti-tumor-, antidepressant-, antivirus-, antibiosis- and anxiolytic-medicine.    ADVANTAGE - The method is capable of simply and easily preparing with high yield of 53.3% and good biological compatibility under mild reaction condition in an eco-friendly manner.    DETAILED DESCRIPTION - Preparing 2-thia-spiro(3.3)hept-6-ylamine hydrochloride salt of formula (I) comprises: adding 7-phenyl-6,8-dioxa-spiro (3.5) nonane-2,2-dicarboxylic acid and pyridine according to a mass volume ratio (g/ml) of 1:5-15 in a reaction vessel to obtain a mixture, reflux heating the mixture for decarboxylation reaction, evaporating under reduced pressure to remove pyridine to obtain residue, adding hydrochloric acid into the residue to adjust pH value to 5-6.8, extracting the residue with a first organic solvent to obtain organic phase, drying the organic phase over anhydrous sodium sulfate, evaporating the organic phase under reduced pressure to obtain 7-phenyl-6,8-dioxa-spiro (3.5) nonane-2-carboxylic acid; adding 7-phenyl-6,8-dioxa-spiro (3.5) nonane-2-carboxylic acid and an alkali solution according to molar ratio of 1:1.1-1.5 into second organic solvent, dropwisely adding diphenylphosphoryl azide (DPPA) to obtain mixture, where volume mass ratio of 7-phenyl-6,8-dioxa-spiro (3.5) nonane-2-carboxylic acid to second organic solvent (g/ml) is 1:5-15, and the molar ratio of 7-phenyl-6,8-dioxa-spiro (3.5) nonane-2-carboxylic acid to DPPA is 1:1-1.5, reacting the mixture at 80-97 degrees C for 0.5-2 hours, adding tert-butanol into the reacted mixture according to molar ratio of 1:3-7, reflux heating for over night, evaporating under reduced pressure to obtain residue, adding the residue into solution of potassium hydroxide having concentration of 5-25% in a volume of 0.3-0.7 times of the volume of the second organic solution, then adding ethyl acetate to extract for obtaining organic phase, washing the organic phase with water and saturated sodium chloride solution, drying over anhydrous sodium sulfate, and evaporating under reduced pressure, purifying the product by a column chromatography to obtain (7-phenyl-6,8-dioxa-spiro (3,5) nonane-2-amino) acid tert-butyl ester; adding (7-phenyl-6,8-dioxa-spiro (3.5) nonane-2-amino) acid tert-butyl ester and palladium carbon catalyst according to mass ratio of 1:0.02-0.1, into third organic solvent to obtain a mixture, where the mass volume ratio (g/ml) of (7-phenyl-6,8-dioxa-spiro (3.5) nonane-2-amino) acid tert-butyl ester to the third organic solvent is 1:10-20, performing reduction reaction to the mixture under the protection of hydrogen, filtering to remove residue for obtaining filtrate, evaporating filtrate under reduced pressure, extracting with petroleum ether, recrystallizing to obtain (3,3-dimethylol-cyclobutyl)-carbamic acid tert-butyl ester; adding (3,3-dimethylol-cyclobutyl)carbamic acid tert-butyl ester and triethylamine according to molar ratio of 1:2-5 into fourth organic solvent to obtain a mixture, cooling the mixture in an ice bath at -10 degrees C, dropping methanesulfonyl chloride into the mixture, where the mass volume ratio (g/ml) of (3,3-dimethylol-cyclobutyl)carbamic acid tert-butyl ester and the fourth organic solvent is 1:5-15, and the molar ratio of (3,3-dimethylol-cyclobutyl) carbamic acid tert-butyl ester to methanesulfonyl chloride is 1:1.5-5, performing mesylation reaction to the mixture under the protection of nitrogen to obtain reacted solution, washing the reacted solution with water, extracting the reacted solution with fifth solvent to obtain organic phase, washing the organic phase with saturated sodium chloride, evaporating under reduced pressure to obtain (3-(tert-butoxycarbonyl-amino) cyclobutane)-1,1-dimethylmethylene sulfonate; adding (3-(tert-butoxycarbonyl-amino) cyclobutane)-1,1-dimethylmethylene sulfonate and sodium sulfide according to a molar ratio of 1:1-1.5 into sixth organic solvent to obtain a mixture, where the mass volume ratio of (3-(tert-butoxycarbonyl-amino) cyclobutane)-1,1-dimethylmethylene to sixth organic solvent is 1:10-20, performing ring closure reaction to the mixture under the protection of nitrogen to obtain reacted solution, washing the reacted solution with water, extracting the solution with ethyl to obtain organic phase, washing the organic phase with saturated sodium chloride, then drying over anhydrous sodium sulfate, evaporating the product under reduced pressure, purifying the product by column chromatography to obtain 2-thia-spiro (3,3) hept-6-carbamic acid tert-butyl ester; and adding 2-thia-spiro (3,3) hept-6-carbamic acid tert-butyl ester and a mixed solution of hydrochloric acid and ethyl acetate according to a molar ratio of 1:5-15 into the reaction vessel to obtain a mixture, cooling the mixture under ice, then reacting the mixture with deprotected tert-butyloxycarbonyl group to obtain reacted mixture, evaporating the mixture under reduced pressure, and recrystallizing to obtain white solid.