Abstract: For investigating the function of the hrpW gene and the nosogenesis of Xcc, in the experiment, an efficient and stable regeneration system was established, by using cotyledonary petioles from 5~6 days’ aseptical plantlets of Brassica napus as explants. Factors affecting transformation of cotyledonary petioles of Brassica napus mediated by Agrobacterium tumefaciens were explored. The hrpW gene of Xanthomonas campestris pv. campestris was transferred into Brassica napus L. by using the method of Agrobacterium tumefaciens mediating. The hrpW gene having been integrated into the genome of Brassica napus L. was confirmed by PCR analysis. The hrpW gene encodes HarpinXcc(Harpin proteid of Xanthomonas campestris pv. Campestris). The obtaining of transgenic plants could be used to investigate the pathogenesis of Xanthomonas campestris pv. Campestris, and that layed a foundation for selecting the rape idioplasm of efficiently resisting disease.