Oilseed rape is very sensitive to most sulfonylurea herbicides. The active constituent of sulfonylurea herbicides is acetolactate synthase(ALS), which catalyzes the common reaction to synthesize three branched-chain amino acids including leucine, valine, and isoleucine in plants. Some sulfonylurea herbicides have strong gametocidal effect on rapeseed. In the present paper, we evaluated the gametocidal effect of 26 herbicides inhibiting the biosynthesis of amino acids after leaf-spraying them at bolting stag...