Abstract: To study the effect of microbial agents in mushroom casing on yield characteristics and microbial diversity, microbial agents were used to deal with Agaricus bisporus casing, and the continuous effects on fruiting bodies and microbial diversity of mushroom casing were observed. The results indicated that spraying both substrate activator A and plant growth regulator B could increase mushroom yield. Using substrate activator A alone, plant growth regulator B alone and the two together increased mushroom yield by 2.89%, 7.27% , 9.22% respectively compared with the control group. Each treatment had little effect on single mushroom weight of 1st flush, but significantly increased the single mushroom weight of 2nd and 3rd flush.Denaturing gradient gel electrophoresis (DGGE) analysis showed that using microbial agents made microbial community of mushroom casing more rich.