Objective To assess the effectiveness and safety of YunNan BaiYao capsules in reducing bleeding quantity during TURP. Methods A double-blind randomized controlled trial was conducted. We randomly allocated 40 patients to the treatment group （ YunNan BaiYao 0.25 g capsule, 2 capsules, q. i. d. , n = 20 ） and the control group （starch capsule, 2 capsules, q. i. d. , n =20）. Patients in both groups were administered three days before operation. Average bleeding quantity, bleeding index of prostate, bleeding intension, length of stay, catheter retention time, and time of washing bladder were observed and compared. Results The average bleeding quantity, bleeding index of prostate and bleeding intension were better in the treatment group than that of the control group with significant difference （P 〈0. 05 ）. The length of stay, catheter retention time and time of washing bladder had no significant difference between the two groups （P 〉0.05）. No obvious adverse effect was observed in both groups. Conclusions YunNan BaiYao capsule can effectively reduce bleeding quantity during TURP without obvious adverse effects.