Objective: To observe the change of nephron damaged by chemotherapy and to evaluate the effect of Baoshen Mixture (保肾合剂, BSM) in protecting and treating damaged nephrons.Methods: Four hundred tumor patients with normal renal function and ready to receive chemotherapy were randomly assigned to two groups. Both groups received one cycle of chemotherapy program of 28-30 days with conventional hydratization, alkalization and chloridization. To the 200 cases in the treated group BSM was given orally thrice a day, 150 mL every time for 15 successive days and the other 200 cases in the control group were treated by chemotherapy alone. The clinical efficacy was compared after treatment, and the changed condition of damaged nephrons were monitored dynamically and compared at different time points (the 3rd, 7th, 14th and 21st day after chemotherapy)by measuring the micro-globulin β2 (β2-MG), albumin (AIb) and immunoglobulin G (IgG) levels in urine with radioimmunoassay (RIA). Results: (1) The effective rates in the treated group at the 4 time points of observation were all higher than those in the control group respectively (P＜0.05 or P＜0.01); (2)Less occurrence of abnormal β2-M, AIb and IgG levels on the 14th and 21st day in the treated group took place compared to that in the control group (P＜0.01); (3) Urinary levels of β2-MG, AIb and IgG reached the peak on the 7th day in both groups, and then, they came down gradually and reted to the normal level on the 21 st day. However, comparison between the two groups showed that all the three parameters in the treated group on day 3, 14 and 21 were lower than the respective one at the corresponding time points in the control group (P＜0.05 or P＜0.01). Conclusion: The chemotherapy damage on nephron is regular in time, and reversible when treated suitably. TCM shows a marked effect in protecting and treating the damage on nephron caused by chemotherapy.