【Objective】A new wild strain of Tricholoma giganteum was identified and the culture medium of mycelium was optimized. 【Method】 The pure mycelium of T. giganteum was obtained from the wild fruitbody by the tissue isolation and identified by molecular biological techniques. The culture condition of the mycelium was researched by measuring mycelial growth rate and growth vigor. The optimum growth medium of mycelium was determined by the uniform-design-method. The method of quadratic polynomial step regression analysis was employed for analyzing the experiment results. 【Result and conclusion】 The wild strain was identified as T. giganteum, named as SCAU3. The accession number of ITS sequence was JX193694 in GeneBank. The results show that the optimum carbon source and nitrogen source for mycelium growth are maltose and yeast extract respectively. The optimum temperature is 30-32 ℃, and the optimum pH in medium was 7-8. The optimum medium for mycelial growth is maltose 26 g·L^-1, yeast extract 2 g·L^-1, MgSO₄ 2.7 g·L^-1, KH₂PO₄ 1.8 g·L^-1, vitamin B1 16 mg·L^-1, pH7.7.