Abstract: The study aims to obtain the transgenic tobacco containing Lchi1 which is the chitinase gene, and detect whether the transgenic tobacco with constitutive Lchi1 gene expression can improve resistance to Valsa ceratosperma, thus to preliminarily determine the function of Lchi1 gene and provide a reference for the further research on molecular breeding about pear Valsa canker. Plant expression vector with gene Lchi1 was constructed and transformed into tobacco by leaf disc mediated with Agrobacterium tumefaciens, and transgenic tobacco T₂ generation was detected by PCR and RT-PCR. The resistance of transgenic tobacco against Valsa ceratosperma was verified more intuitively by isolated leaf inoculation method. Lchi1 was integrated into tobacco genome, and it was expressed effectively in the transgenic tobacco T₂ generation. After inoculating Valsa ceratosperma, the resistance of transformant against Valsa ceratosperma was obviously more enhanced compared with non transgenic tobacco. In conclusion, Lchi1, which is the pear chitinase gene, is associated with the resistance of pear Valsa canker, and it will be used as an important genetic source in the research of molecular resistance breeding.