[Objective] The aim was to select and purify the dominant endophytic fungus from cotton.[Method] With cotton seedlings as the tested material,after their leave surfaces were thoroughly disinfected,their tissue homogenate was coated on different medium plate,the morphologies of the cultured colonies were observed and the colonies with different morphologies were selected.After that,the colonies were purified with streak plate,examined by microscopic and preserved on inclined plane with low temperature and th...