Use of Fructus schisandrae in preparation of medicaments for preventing and reducing toxicity and side effects of antineoplastic agents. The toxicity and side effects of antineoplastic agents are cardiovascular toxicity, hepatotoxicity, nephrotoxicity, suppression of bone marrow, immunosuppression, or alopecia etc induced by antineoplastic agents. Fructus schisandrae and extracts thereof, especially ethanol extracts, schisandrin B, are effective in reducing antineoplastic agent's toxicity and side effects.