Abstract: Biocontrol agent Pseudomonas fluorescens 2P24, one of plant growth-promoting rhizobacteria (PGPR), possesses a type-Ⅲ secretion system (T3SS) for association with plants. To enable 2P24 to express a harpin protein which triggers hypersensitive response (HR) in plants and to have the ability to induce resistance to plant pathogen infection, we constructed a fusion of a hap1 gene, which encodes a harpin of Xanthomonas oryzae pv. oryzicola, with a promoter of avrPto1 of Pseudomonas syringae pv. tomato DC3000 which was induced in 2P24. This recombination led 2P24 to express the harpin protein Hpa1. The protein, secreted via the T3SS of 2P24, triggered HR in tobacco via the activation of HR marker genes, HIN1 and HRS203J, and pathogenesis-related protein gene PR1a. The genetic modified 2P24 with the harpin coding gene, as the recipient strain 2P24, had antimicrobial ability against wheat scab Fusarium graminearum and cotton wilt F. oxysporum f. sp. vasinfectum. Using HR-elicitors from plant-pathogen interactions to genetically modify biocontrol antimicrobes provides a fundamental basis for plant disease control.