Carboxymethyl chitosan-castor oil-based polyurethane microspheres (CO-CMCS-PU) were prepared from carboxymethyl chitosan (CMCS), castor oil (CO) and isophorone diisocyanate (IPDI) by self-emulsification, and drug-loaded microspheres (CO-CMCS-PU@AVM) were obtained by loading avermectin (AVM) by molecular self-assembly. The structure and morphology of the product were characterized by FTIR, 1HNMR, SEM and TGA, and the encapsulation efficiency, slow-release performance, anti-ultraviolet performance, leaf contact angle and adhesion performance of drug-loaded microspheres with different doses were explored. The results showed that compared with AVM dispersion, the retention rate of AVM in drug-loaded microspheres increased to 43% after ultraviolet irradiation, which indicated that CO-CMCS-PU carrier had good ultraviolet resistance. Compared with AVM dispersion, the contact angle of drug-loaded microspheres on cucumber leaves decreased by more than 20%, and the retention capacity increased by more than 40%, which indicated that they had good adhesion and wettability on cucumber leaves. The encapsulation efficiency of drug-loaded microspheres can reach more than 80%, which has good slow-release and pH-responsive release performance. The drug release behavior conforms to the First-order kinetic model, and the drug release is controlled by Fickian diffusion.