Plant height is mainly confined by stem elongation,which is not only a decisive factor that affects plant architecture but also contributes to crop yield.Although many studies on the genetic basis of plant height have been done in rice,wheat and other important crops,less has been done in the allotetraploid oilseed rape.In this study,we identified a novel rapeseed mutant named as BnA3.dwf with greatly decreased height from mutation library by EMS.The BnA3.dwf displayed several mutant phenotypes compared with wild at seedling stage including hypocotyl,leaf and growth.At mature stage,the mean height of mutant plants was only about half of the wild-type plants.