To assess the efficacy and mechanism of circumcision in the treatment of premature ejaculation (PE) with redundant prepuce, we enrolled a total of 81 PE patients who received circumcision. The patients' ejaculatory ability and sexual performances were evaluated before and after circumcision by using questionnaires (Intravaginal ejaculation latency time (IELT), Chinese Index of PE with 5 questions (CIPE-5) and International Index of Erectile function- 5 (IIEF-5)). Furthermore, somatosensory evoked potentials (SEPs) including dorsal nerve (DNSEP) and glans penis (GPSEP) of the patients were also measured. The mean IELTs of preoperation and post operation were 1.10 ± 0.55 and 2.48 ± 2.03 min, respectively (P < 0.001). In addition, the geometric mean IELT after operation was 2.16 min, compared with the baseline 1.07 min before the operation, the fold increase of the IELT was 2.02. Compared with the uncircumcised status, scores of CIPE-5 showed a significant increase after circumcision (P < 0.001). The mean latencies (and amplitudes) of GPSEP and DNSEP were 38.1 ± 4.0 ms (3.0 ± 1.9 uV) and 40.5 ± 3.4 ms (2.8 ± 1.6 uV) before circumcision, respectively; and 42.8 ± 3.3 ms (2.8 ± 1.6 uV) and 40.5 ± 4.1 ms (2.4 ± 1.2 uV) in the follow-up end point after circumcision. Only the latencies of GPSEP showed significant prolongation before and after circumcision (P < 0.001). The ejaculation time improvement after circumcision is so small, and equal to placebo response, therefore it could not be interpreted as a therapeutic method in men with PE.