Objective To evaluate the efficacy of ultrasound-guided obturator nerve block using proximal interfascial technique.Methods Seventy ASA physical status Ⅰ or Ⅱ patients of both sexes, aged 43-82 yr, with body mass index of 18.0-30.5 kg/m2, scheduled for elective trans-urethral resection of bladder tumor, were randomly divided into 2 groups (n =35 each) using a random number table: remote interfascial technique group (group R) and proximal interfascial technique group (group P).In group R, interfascial injections at 2 planes, lateral and deep to the adductor brevis muscle, were carried out with 0.375％ ropivacaine 7.5 ml to block each obturator nerve branch separately.In group P, 0.375％ ropivacaine 15.0 ml was injected under ultrasound guidance at the interfascial plane inferior to the superior pubic ramus (between the pectineus and obturator externus).The strength of thigh adduction was measured before injection (baseline) and at 5, 10, and 15 min after injection.Then combined spinal-epidural anesthesia was performed at L3,4 interspace.The 50％ strength reduction indicated a successful block.The block performance time was recorded.The success rate of block at 15 min after injection was calculated.It was considered clinically effective when obvious muscle twitching interfering with the surgical procedure did not appear.The clinical outcome was assessed, and the effective rate of clinical outcome was calculated.Results Compared with group R, the block performance time was significantly shortened, the success rate of block, strength reduction at 10 and 15 min after injection, and clinical outcome were increased in group P.There were no significant differences in the effective rate of clinical outcome.Conclusion Compared with remote interfascial technique, ultrasound-guided obturator nerve block using proximal interfascial technique provides easier and rapid procedure, higher success rate of block and better clinical outcome of block.