A sulphonylurea herbicide,monosulfuron-ester sodium,was first used to induce male sterility of rapeseed(Brassica napus L.).The plants sprayed once with 10ml×0.05-0.1 μg/ml monosulfuron-ester sodium solution per plant in uninucleate stage of the longest buds,resulted in nearly 100%male sterility in “zhongshuang No.9” and “zhongshuang No.11”,with no adverse effects on main agronomic features and female fertility observed.Forty-nine different genotypes of rapeseed were treated with 10ml×0.1μg/ml monosulfuron-ester sodium solution per plant,resulting in 48 genotypes male sterility,and seven of these 48 genotypes could be male sterile for the whole flowering period.Seed yield of these monosulfuron-ester sodium treated rapeseeds were not significantly reduced compared with the Control as determined by seed number per plant.The hybridity of seeds from line ZS09 treated with 10ml 0.1μg/ml×2 monosulfuron-ester sodium solution per plant and pollinated by a male line SH11 was 95.5%tested by SSR technique,which met the hybridity requirement in China.The results suggest that monosulfuron-ester sodium could be used as an efficient chemical hybridizing agent for B.napus.