Abstract: The study aims at the influence of microorganisms in the process of Agaricus bisporus compost primary fermentation on its physical and chemical properties. Research was carried out on the variation of microbial population, pure protein, total sugar, lignin, cellulose, hemicellulose, microelement, temperature and pH indicators in the process of Agaricus bisporus compose fermentation. With the fermentation conducted, the amount of three categories of microorganisms, including bacteria, actinomycete and fungus, all showed that an increasing trend at first increased and then a downward trend. Pure protein was on the raise; total sugar, cellulose and hemicellulose were on downward trend, the temperature and pH of compost showed cyclical variations during the fermentation period, increased and decreased with turning heaps. The variation of zinc content of microelement did not increase significantly, iron, copper and manganese content rose as fermentation of compost. The variation characteristics of the microorganisms and partials physicochemical indices in the Agaricus bisporus compost were obtained, which provided theoretical basis for studying the highefficient fermentation of Agaricus bisporus compost.