NOVELTY - Sustained-release fertilizer comprises sodium sulfate, potassium nitrate, ammonium phosphate, rapeseed cake, orange core powder, chicken bone meal, urea, microbial layer, chelation layer, microcrystalline rock phosphate coating layer, and suitable quantity of water, where the microbial layer comprises effective microorganism (EM) microbial inoculants, diatomite, and sugar water.    USE - The sustained-release fertilizer is useful for crop.    ADVANTAGE - The sustained-release fertilizer exhibits synergistic effect, converts nitrogen into ammonium and nitrate, is easily absorbable, and improves utilization rate of nitrogen.    DETAILED DESCRIPTION - Sustained-release fertilizer comprises 1-3 pts. wt. sodium sulfate, 4-5 pts. wt. potassium nitrate, 8-10 pts. wt. ammonium phosphate, 27-30 pts. wt. rapeseed cake, 14-15 pts. wt. orange core powder, 18-20 pts. wt. chicken bone meal, 18-22 pts. wt. urea, 2-4 pts. wt. microbial layer, 4-5 pts. wt. chelation layer, 6-9 pts. wt. microcrystalline rock phosphate coating layer, and suitable quantity of water, where the microbial layer comprises 5-7 pts. wt. effective microorganism (EM) microbial inoculants, 45-55 pts. wt. diatomite, and 120-140 pts. wt. sugar water. The EM microbial inoculants is prepared by adding sugar water to microbial inoculants, uniformly stirring to obtain microbial liquid, soaking diatomite in sulfur acid solution for 60 minutes, washing soaked diatomite with neutral water, drying washed diatomite at 400-500 degrees C for 2-3 hours, cooling dried diatomite at room temperature, grinding dried diatomite into fine powder, adding microbial liquid, uniformly stirring for 20-30 minutes, filtering fine powder particle, and drying filtered fine powder particle using air blower at 30-40 degrees C. The chelation layer is prepared by weighing 24-26 pts. wt. attapulgite, 16-18 pts. wt. abandoned animal fur, 4-7 pts. wt. ferrous sulfate, and 3-5 pts. wt. zinc sulfate, sintering attapulgite at 600-800 degrees C for 2 hours, grinding into fine powder, adding 6-8 mol/l hydrochloric acid to abandoned animal fur, hydrolyzing for 18-24 hours, adding limewater to neutralize pH 7, filtering mixture, adding ferrous sulfate to the filtered liquid, heating and sintering at 40-60 degrees C for 1-2 hours, adding zinc sulfate, sintering at 50-80 degrees C for 1.5-3 hours, adding attapulgite powder to the sintered liquid, and drying and crushing the to obtain complex sintered powder. The microcrystalline rock phosphate coating layer is prepared by weighing 28-32 pts. wt. rock phosphate, 8-10 pts. wt. cattle bone glue, and suitable quantity of water, vibrating rock phosphate to obtain superfine microcrystalline powder, adding cattle bone glue, and suitable quantity of water, uniformly mixing, soaking for 8-10 hours, heating the mixture at 70-80 degrees C and uniformly stirring the mixture. An INDEPENDENT CLAIM is included for method for preparing sustained-release fertilizer, which involves (a) placing rapeseed cake, orange core powder, and chicken bone meal in a pool, adding suitable quantity of water, fermenting for 3-4 weeks, drying the fermented product and crushing dried fermented product, (b) uniformly spraying microcrystalline coating layer on phosphate rock, heating to melt the outer surface, and forming inner layer, (c) uniformly mixing ammonium phosphate and urea, adding suitable quantity of water, uniformly stirring the mixture into granule, centrifuging the mixture at 80-120 revolutions/minute (rpm) for 15-20 minutes, adding chelation layer, centrifuging again at 200-240 rpm for 10-12 minutes, and forming middle layer agent, and removing and drying the granule, (d) adding sodium sulfate, potassium nitrate and suitable quantity of water, uniformly spraying on the outer surface of granule, adding microbial layer and remaining raw materials, uniformly mixing, and forming outside layer, and (e) drying the resulting granule at 40-50 degrees C, weighing and packing the dried granule.