Clinical data of 120 patients undergoing transurethral resection of the bladder sidewall tumors (TURBt) were retrospectively analyzed.Before TURBt the obturator nerve was blocked under the guide of the nerve stimulator in 46 cases (block group) and not blocked in 74 cases (unblock group).The incidence of obturator nerve reflex and bladder perforation in block group was significantly lower than that in unblock group(7％ vs.35％,P =0.000 and 0 vs.19％,P =0.002,respectively).The operation time and the duration of bladder continuous saline irrigation after operation in block group were shorter than those in unblocked group [(32.2 ± 12.5) vs.(43.2 ± 24.5) min,P =0.001 and (8.9 ± 6.4) vs.(13.3 ±10.8) h,P =0.013,respectively].The efficiency value of TURBt in block group was better than that in unblock group [(5.8 ±3.9) vs.(9.3 ± 7.0) min/cm2,P =0.001].The obturator nerve block guided by the nerve stimulator can improve the safety and the efficiency of TURBt.