The invention provides a benazolin / metazachlor weedicide composition, belonging to the improved weedicide compositions. The invention also provides a preparation method and application of the composition. The composition is a mixture of a compound (A) benazolin and a compound (B) metazachlor and can effectively prevent and kill off the annual grass weeds, such as crabgrass, barnyard grass, bluegrass, green bristlegrass and the like, and the broadleaf weeds, such as amaranthaceae, chamomile, matricary, polygonaceae, mustard, solanaceae, chickweed, catchweed bedstraw, xanthium sibiricum patrin,amaranthus ragweed, smartweed, speedwell and the like. The control effect of the composition is obviously better than that of the single compound (A) or compound (B), thus substantially reducing the application dosage of various active substances.