In order to identify effects of the cross-resistance and the function of resistant genes BnAHAS1-3R in germplasm M196， this study examined the resistance effect of rapeseed M196 and N131 （wild type） by spraying sulfonylurea， sulfonlyaminocarbonyl-triazolinone， imidazolinone， triazolopyrimidine， and pyrimidyl-benzoate with different concentration gradients （0， 1/4， 1/2， 1， 2 and 4 times the recommended concentration of herbicides in the field）， respectively， at 3-5 leaf stage. Based on the greenhouse and field results， the cross-resistance of SU and SCT was observed simultaneously to be the strongest， while IMI， TP and PB were lower. Results of qRT-PCR and in vitro enzyme inhibition experiments in transgenic Arabidopsis indicated that the cross-resistance of ALS herbicides was caused by the elevated expression of the mutated allele of BnAHAS1-3R and the decrease on enzyme sensitivity to herbicides. The study provides a theoretical basis for preventing and resolving the potential problems about weed resistance and drift of resistance gene that may arise from the widespread promotion of resistant varieties.