Objective To evaluate the efficacy and safety of solifenacin in the prevention of bladder spasm after urethroplasty.Methods From July 2011 to May 2012,120 cases after the urethroplasty were assigned into the study group (n =64) and control group (n =56),based on simple randomization (coin toss).Patients in the study group were treated with solifenacin (5 mg once daily) for a seven days period beginning the first day after operation.Patients in the control group were treated with placebo during the seven days.Each group was further divided into four subgroups:paracentetic suprapubic cystostomy subgroup (study group 10 patients/ control group 1 0 patients),traditional suprapubic cystostomy subgroup (study group 15 patients / control group 13 patients),urethral catheter subgroup (study group 10 patients/control group 12 patients),former suprapubic cystostomy subgroup (study group 29 patients/control group 21 patients).Visual analogue scale (VAS) was used to measure the severity of bladder spasm.The mean duration of spasm,the frequency of spasm,the incidence of urine extravasation and radiating pain were recorded each day.Besides these,the side effect after using solifenacin was also noticed.Results There were no significant difference in the VAS scores and mean duration of bladder spasm between study group and control group (P>0.05).However,there was a significant low VAS scores to those taking solifeuacin in paracentetic suprapubic cystostomy subgroup (1.27,1.58,1.13,1.23,1.17,1.00,0.53) than those in the control group (4.10,4.12,3.80,3.22,3.22,3.17,2.22) (P<0.05).Similar tendency could be noticed in the mean duration of bladder spasm in this subgroup within 4 days,while the significant difference was not noticed in this comparison.ln the comparison of daily and night frequency of spasm within four subgroups,significant difference was noticed in the control group within 6 days.The similar difference was not noticed within 6 days in the study group.No significant diffference was found between study and control group in urine extravasion and radiating pain.In study group,dry mouth was found in 3 patients and constipation in 5 patients.In control,constipation was found in 6 patients.Conclusions Solifenacin can effectively reduce the frequency of bladder spasm after the urethroplasty.Patients who accept the aracentetic suprapubic cystostomy might be the most optimal group for using this medicine. Key words: Solifenacin; Urethroplasty; Bladder spasm; Prospective studies