Background Occult stress urinary incontinence may lead to de novo stress urinary incontinence after pelvic floor repair surgery.A measurement of pudendal nerve terminal motor latency can reflect the integrity of the nerves.We aimed to explore the value of pudendal nerve terminal motor latency in the diagnosis of occult stress urinary incontinence in pelvic organ prolapse patients.Methods Ten patients with stress urinary incontinence (SUI group),10 with SUI and uterine or vaginal prolapse (POP+SUI group) and 10 with uncomplicated uterine or vaginal prolapse (POP group) were evaluated for their pudendal nerve terminal motor latency using a keypoint electromyogram.Results The amplitude of positive waves was between 0.1 and 0.2 mV.The nerve terminal motor latency was between 1.44 and 2.38 ms.There was no significant difference in the wave amplitudes of pudendal nerve evoked action potential among the three different groups (P ＞0.05).The pudendal nerve latency of the SUI group,POP+SUI group and POP group were (2.9±0.7) seconds,(2.8±0.7) seconds and (1.9±0.5) seconds respectively.The difference between the SUI group and POP+SUI group was not statistically significant (P ＞0.05),whereas the difference between the SUI and POP groups and between the POP+SUI and POP groups were statistically significant (P ＜0.05).There was a positive correlation between pudendal nerve latency and the severity of SUI; the correlation coefficient was 0.720 (P ＜0.01).Conclusions Patients with SUI may have some nerve demyelination injuries in the pudendal nerve but the damage might not involve the nerve axons.The measurement of pudendal nerve latency may be useful for the diagnosis of SUI in POP patients.