A mushroom growth promoting agent is disclosed. A preparation method of the mushroom growth promoting agent includes the following steps: providing a sawdust waste, mixing the sawdust waste with water to form a first mixture, and extracting the first mixture to obtain a first supernatant. The first supernatant contains the mushroom growth promoting agent.本發明提供一種菇類生長促進物,其係以下列步驟所得:提供一廢棄木屑,將廢棄木屑與水混合成第一混合物,最後對第一混合物進行粗萃取步驟,以獲得第一上清液,其中第一上清液包含菇類生長促進物。本發明另提供一種前述菇類生長促進物之製備方法及應用其之菇類液態培養基。110‧‧‧步驟120‧‧‧步驟130‧‧‧步驟
