Cyclophosphamide is a very classic drug for treating nephritis. These drugs belong to alkylating agents in immunosuppressants and have good effect on many types of nephritis, such as lupus nephritis, ANCA-associated vasculitis and membranous nephropathy. Especially in combination with glucocorticoids, it can cure many nephritis. However, the side effects of cyclophosphamide are relatively large. The common more serious side effects include bone marrow suppression, bladder toxicity, gonadal toxicity and carcinogenic risk. Bone marrow transplantation is dose-dependent and requires regular blood tests to prevent myelosuppression. Bladder toxicity is mainly manifested as hemorrhagic cystitis, so patients treated with cyclophosphamide need to drink more water and hydrate adequately to reduce bladder toxicity.