Objective: To evaluate the efficacy and safety of sodium copper chlorophyllin (trademarked and five patients with leukopenia caused by various factors were randomized into 3 groups. The 60 patients in the YBK group took orally YBK Tablets at the dose of 40 mg, three times per day, the 30 patients in the leuthe 15 patients in the placebo group were administered with vitamin C tablets 100 mg, three times per day.All the subjects were treated for 1 month. The change of peripheral leucocytes count after treatment and adverse drug reaction that occurred in patients were studied. Results: In the 60 patients treated with YBK, the treatment proved to be markedly effective in 34 cases, effective in 17 and ineffective in 9, the total effective rate being 85%, which was significantly higher than that in the placebo group (26.7%, P＜0.01) and similar to that in the leucogen group (83.3%, P＞0.05). No adverse reaction was found in the treatment course.Conclusion: YBK can be used in the treatment of leukopenia caused by various factors, satisfactory in efficacy and safe in use.