Abstract: Objective To observe the changes of auditory steady-state response (ASSR) threshold in guinea pigs with posterior semicircular canal fistula. Methods In 10 guinea pigs, a window was opened in the posterior semicircular canal of the left ear with the right ear serving as the control for testing the ASSR under anesthesia with pentobarbital sodium. Results The mean and standard deviation of ASSR threshold (dB SPL) at 0.5, 1, 2, and 4 kHz in the left ear was 35.00±14.33, 25.50±12.37, 20.00±9.37 and 20.00±9.18, respectively, and was 31.00±16.19, 25.50±12.34, 18.00±6.96 and 18.50±6.71 in the right ear, respectively. Paired-sample t test showed no significant difference in the ASSR at the same frequency between the two ears. Conclusion Small fistula by surgery causes no significant hearing loss in guinea pigs.