The invention relates to a new medical use of astaxanthin, i.e. prevention and treatment of organophosphorus pesticide induced male reproductive toxicity, and further relates to application in drugs inhibiting organophosphorus pesticide induced sperm motility decrease, sperm abnormality rate increase, testis tissue MDA content increase, and testis tissue CAT activity and LDH activity decrease. High-toxic organophosphorus pesticide and low toxicity organophosphorus pesticide phoxim are adopted as the representative to study the prevention and treatment effect of astaxanthin on male reproductive toxicity caused by low concentration organophosphorus pesticide exposure, and the study proves that astaxanthin can inhibit male reproductive toxicity induced by organophosphorus pesticide and has good dose dependence, thus putting forward application of astaxanthin as an active material in preparation of drugs for organophosphorus pesticide induced male reproductive toxicity.