NOVELTY - Preparing chiral cyclic N,N-acetal compound (I) comprises reacting o-formyl benzoate and N-substituted aliphatic diamine as raw material, in the presence of an organic solvent and optionally 3 Angstrom , 4 Angstrom or 5 Angstrom zeolite at 85-100 degrees C, then carrying out condensation reaction in the presence of chiral Bronsted acid catalyst (II) or a chiral oxazoline/a metal salt as a catalyst, amidation reaction for 5 minutes to 72 hours and isolating product. The molar ratio of o-formyl benzoate, N-substituted aliphatic diamines and chiral catalyst is 1:1.2-2:0.02-0.2.    USE - The method is useful for preparing (I) (claimed), which is useful as intermediate for preparing medicine.    ADVANTAGE - The method is capable of preparing (I) with high yield, good selectivity, under mild condition, in a simple and eco-friendly manner.    DETAILED DESCRIPTION - Preparing chiral cyclic N,N-acetal compound of formula (I) comprises reacting o-formyl benzoate and N-substituted aliphatic diamine as raw material, in the presence of an organic solvent and optionally 3 Angstrom , 4 Angstrom or 5 Angstrom zeolite at 85-100 degrees C, then carrying out condensation reaction in the presence of chiral Bronsted acid catalyst (II) or a chiral oxazoline/a metal salt as a catalyst, amidation reaction for 5 minutes to 72 hours and isolating product. The molar ratio of o-formyl benzoate, N-substituted aliphatic diamines and chiral Bronsted acid catalyst is 1:1.2-2:0.02-0.2.    R1 = H, 1-16C-alkyl, 2-16C-alkenyl, 2-16C-alkynyl, 3-16C-cycloalkyl, 3-16C-cycloalkenyl, 3-16C-alkynyl, 2-16C-carbonyl, aryl, heteroaryl, or monovalent group of formula (a);    R2-R5 = H, F, Cl, Br, I, 1-16C-alkyl, 1-16C-alkoxy, 2-16C-alkenyl, 2-16C-alkynyl, 3-16C-cycloalkyl, 3-16C-cycloalkenyl, 3-16C-cycloalkynyl, 2-16C-carbonyl, CN, NO2, SO3H, aldehyde, OH, carboxyl, amino, amide, aryl, heteroaryl or (a);    R6-R9 = H, 1-16C-alkyl, 2-16-alkenyl, 2-16C-alkynyl, 3-16C-cycloalkyl, 3-16C-membered ring, O, or (a);    R10 = H, 1-16C-alkyl, 3-16C-alkenyl, 3-16C-alkynyl, 3-16C-cycloalkyl, 3-16C-cycloalkenyl, 3-16C-cycloalkynyl, aryl, heteroaryl or (a);    R11-R15 = H, 1-16C-alkyl, 2-16C-alkenyl, 2-16C-alkynyl, 3-16C-cycloalkyl, 3-16C-cycloalkenyl, 3-16C-cycloalkynyl, CN, NO2, CF3, SO3H, aldehyde, OH, carboxyl, amino, aryl, heteroaryl or 2-formyl-benzoic acid of formula (b);    R16 = 1-16C-perfluoroalkyl, 1-16C-alkyl, 2-16C-alkenyl, 2-16C-alkynyl, 3-16C-cycloalkyl, 3-16C-cycloalkenyl, 3-16C-cycloalkynyl, heteroaryl, conjugated aryl or phenyl group of formula (c); and    n = 0-4, where the aryl is substituted with phenyl, the conjugated aryl is phenanthryl and anthryl, and the 5-10C heteroaryl optionally comprises N, S or O.