The invention discloses a plant pathogen inhibitor and a strain involved therein and an application of the plant pathogen inhibitor. The strain is streptoverticillium davidii T22 which is registered in the General Microbiology Center of the China microbial species Preservation and Management Committee with the number of CGMCC No. 14190. The streptoverticillium davidii T22 has inhibitory effect on botrytis cinerea, peach brown rot and capsicum anthracnose in fruits and vegetables, streptoverticillium davidii T22 aseptic fermentation filtrate can effectively inhibit the hyphal growth of strawberry gray mold, tomato gray mold and cucumber fusarium wilt, and the streptoverticillium davidii can form hydrolysis cycles on the medium for enzyme activity detection by producing cellulase and chitinase. Obviously, the streptoverticillium davidii T22 can inhibit plant pathogenic fungi by producing antibiotic-like active substances and hydrolase-like substances; proper dilution of the streptoverticillium davidii T22 aseptic fermentation filtrate can significantly promote the extension of tomato hypocotyl and/or radicle and enhance the germination potential of tomato seeds.