The application discloses a trichoderma polysporum fungus and application thereof to biologial weeding. A strain of the trichoderma polysporum fungus is named in a classified mode as trichoderma polysporum, is completely named as trichoderma polysporum HZ-31, is preserved in China General Microbiological Culture Collection Center on September 12, 2016, and has a preservation number of CGMCC No.12867. The invention provides wettable powder consisting of trichoderma polysporum fungal spore powder obtained by fermenting 10 to 15% of kaolin, 6% of polyvinyl alcohol, 3% of dextrin, 3% of nekal, 1% of bentonite and solid. According to the invention, aiming at common weeds in broad bean and pea fields, such as avena fatua, persicaria lapathifolia, lepyrodiclis holosteoides, chenopodium album, elsholtzia densa, and polygonum aviculare, the trichoderma polysporum fungus wettable powder is prepared, is used for biological weeding, can effectively and safely control, prevent and treat part of common farmland weeds, is low in cost, has no pollution, and is low in residue and environmental-friendly.