Cucumber Corynespora leaf spot caused by Corynespora cassiicola has become an important new epidemic disease in cucumber production in China．At present，there is no resistant varieties and the infection mechanism of C. cassiicola and its interaction with host are still unknown．In order to investigate the pathogen of C. cassiicola，the RFP-labeled transformant was generated with Agrobacterium tumefaciens-mediated transformation（ATMT）．The transformant was able to emit strong red fluorescence on mycelia and conidia during 6 passages of transformants on PDA．The biological determination and pathogenicity test demonstrated that there was no significant differences between the wild strain and the transformant．