[Objective] The screening method and the pathogenic function of pathogenic bacteria X46（Micromonospora）of crabgrass was studied.[Method] Improved Gaoshi No.I medium was adopted to isolate a strain of pathogenic bacteria X46 of crabgrass from the rhizosphere soil of crabgrass and barnyardgrass,the optimal toxin production condition was determined,and the preliminary assessment of its security was conducted.[Result] Pathogenic bacteria X46（Micromonospora）of crabgrass was identified to be Micromonospora.When the liquid volume of 300 ml flask was 30 ml,initial pH was 6.0-6.5,inoculation amount was 10%,fermentation was conducted at 180 r/min,28 ℃ for 120 h,the production amount of toxin in improved Gaoshi No.I medium was the largest,these were the optimum culture condition.The bacteria had significant promotion effect on the growth of maize,tomato and soybean,which had slight inhibition effect on wheat growth and significant inhibition effect on cucumber growth.[Conclusion] X46 is a potential strain that can be developed as the biological herbicide in North China.
