Abstract: 【Objective】 In this study, the pathogenicity of Agrobacterium tumefaciens, a pathogen isolated from tumor tissues collected from several peach production regions, was identified. 【Method】Molecular detection of virD2 and ipt genes associated with A. tumefaciens and T-DNA metastasis and gall tumor formation was carried out. The pathogenicity of A. tumefaciens isolated from tumor tissues collected from different peach production regions was identified by means of the 3-ketoglycosides test and other biological methods. Indicator plants were used to detect the pathogenicity of strains of different biological types. Finally, peach plants of different varieties was used to verify the pathogenicity of crown gall strains by artificial inoculation. 【Result】 The PCR results showed that there are both 203 bp and 427 bp target fragments of the specific primers virD2 and ipt genes in 21 strains of pathogenic bacteria, Which indicate that the isolated pathogens belong to A. tumefaciens. The results of 3-ketoglycosides test show that 3 strains changed from blue to yellow belong to Biotype Ⅰ , and the remaining 18 strains with unchanged color belong to Biotype Ⅱ . Indicator plants show that pathogens could form tumors on plants, and the pathogenicity of Biotype Ⅱ strains is significantly stronger than that of Biotype Ⅰ . The inoculation of Biotype Ⅱ pathogens in different varieties of peach trees can form tumors obviously, and it also verify that Biotype Ⅱ pathogens have stronger pathogenicity. 【Conclusion】 The pathogens of crown gall disease isolated from different peach production areas are A. tumefaciens, most of which belong to Biological biotype Ⅱ , which has strong pathogenicity and can infect almost all peach varieties.