In order to obtain the proper spawn fitting for industrial cultivation of Agaricus bisporus,the study was carried out to increase the mycelium biomass and control the hyphal ball diameter and density in submerged culture process.Using Agaricus bisporus As2796 as the strain,the single factor tests and orthogonal design method were employed to optimize medium composition and its liquid culture condition in the trial.The results showed that the optimum medium composition for culturing Agaricus bisporus primary spawn in liquid was as follows: potato 80 g,brown sugar 12 g,glucose 9.0 g,peptone 2 g,yeast extract 1 g,KH2PO4 2 g,MgSO4·7H2O 1 g,and VB1 0.01 g in 1 000 mL water.The best liquid culture conditions for secondary spawn were as follows: shaking speed of 150 r/min,culture temperature 25℃,initial pH 6.0,inoculation quantity 12%,and filling with 100 mL fluid in 250mL flask.Under the conditions,the hypha ball diameter could be controlled effectively in the range of 1.5 mm to 2.0 mm,and mycelium biomass yield reached 25.0 mg/mL(on a dry-weight basis).