Abstract: In order to further understand the biological characteristics of Lyophyllum decastes and select the appropriate formula of mother culture medium, the screening tests of different carbon sources, nitrogen sources, pH and temperature conditions were set up to observe the mycelial growth and microstructure of Lyophyllum decastes. The results showed that the optimum carbon source was starch, the optimum nitrogen source was sodium nitrate, the optimum pH was 7.0, and the optimum temperature for the mycelial growth was 25℃. The mycelium of Lyophyllum decastes was a binuclear cell with clamp connection. Its cells were longer, and the visibility of cell membrane was different at different growth stages.