Abstract: In digital hearing aids, wide dynamic range compression algorithm (WDRC) is commonly treated as the core algorithm to compensate loudness. Differences between release time constants in WDRC can affect speech intelligibility (SI). Based on unique acoustic characteristics of Mandarin, WDRC algorithm are divided into two parts: low frequency (LF) channel and high frequency (HF) channel. Release time constants are taken as 5 ms, 100 ms, and 2000 ms in either LF channel or HF channel. Combining a certain LF release time constant with a certain HF one forms totally nine different release time combinations for hearing tests. Normal hearing objects go through the Mandarin SI tests with speech shaped noise. The testing material is Mandarin sentences which are the outputs of WDRC simulation in the 9 different release time combinations. Test results show that too short release time in LF channel or too long release time in HF channel trends to decrease Mandarin SI. The results can be a reference for WDRC parameter setting of Mandarin speaker.