NOVELTY - A controllable light degradation nanometer avermectin microcapsule (M1) is prepared by (A) recrystallization of avermectin pesticide crystal, (B) preparation of nanometer avermectin by layer-layer self-assembly method, (C) preparation of light degradation carrier. The step (C) includes obtaining nanometer titanium oxide (TiO2) by concentrated titanium sulfate by hydrolysis, condensation, crystal adding and roasting; and mixing light catalyst and nanometer avermectin and adsorbing to obtain light degradation nanometer avermectin.    USE - Method is used for preparation of controllable light degradation nanometer avermectin microcapsule (M1) (claimed) for green pesticide.    ADVANTAGE - The method is simple, and has mild reaction condition, easy operation and good repeatability.    DETAILED DESCRIPTION - Controllable light degradation nanometer avermectin microcapsule (M1) is prepared by (A) recrystallization of avermectin pesticide crystal, (B) preparation of nanometer avermectin by layer-layer self-assembly method, (C) preparation of light degradation carrier. The step (A) includes dissolving avermectin pesticide (0.1-1 g) in organic solvent (50 mL), and magnetically stirring for 1 hour adding deionized water (200 mL) containing 0.025 % (m/v) hydroxypropyl methyl cellulose (HPMC), and magnetically stirring, where particle size of the avermectin pesticide of 0.1-100 mu m is regulated by probe ultrasonic wave, and ultrasonic time is 0-10 minutes; and obtaining avermectin pesticide recrystallization crystal. The step (B) includes dispersing avermectin pesticide recrystallization crystal (10-100 mg) in deionized water (500 mu L), and adding 1 mL anion polyelectrolyte chitosan solution (0.5-5 mg/L), and ultrasonically adsorbing for 5-15 minutes; and adding 1 mL cation polyelectrolyte algin solution (0.5-5 mg/mL)m, 2 times centrifuging, and adsorbing for 5-15 minutes, where chitosan and algin are adsorbed gradually in layer to obtain 5-10 layers of core-shell structure nanometer avermectin microcapsule. The step (C) includes:    (A) obtaining nanometer titanium oxide (TiO2) by concentrated titanium sulfate through steps of hydrolysis, condensation, crystal adding and roasting;    (B) regulating pH value, and adding silver nitrate solution (0.01-0.05 mol/L);    (C) passing hydrogen gas to reduce silver ion and prepare silver/TiO2;    (D) mixing nanometer TiO2 and sodium tungstate dihydrate (2-4 g), and adding into distilled water (100 mL) to prepare mixed solution;    (E) stirring for 0.1-1 hour by magnetic stirrer, and treating with high pressure, where sample is dried to obtain W/TiO2;    (F) mixing light catalyst and nanometer avermectin and adsorbing to obtain light degradation nanometer avermectin.