Abstract: [Objective]The genetic transformation of Valsa mali var. mali was developed by PEG-mediated protoplasts transformation.[Method]It was transformed by PEG-induced fusion of protoplasts. The plasmid pBIG2RHPH2-GFPGUS carrying hph gene was used and Valsa mali var. mali 03-8 isolate was used as the host strain.[Result]At50 mg/mL driselase + 10 mg/mL lysing enzymes concentration,the mycelium of Valsa mali var. mali cultured in YEPD medium for 48 h was hydrolyzed in 10 mL enzymes liquid /0. 5 g wet mycelium for 2 h. The protoplast yield was 4×107 CFU /mg. The transformation efficiency was 44 per g DNA. Analysis of the transformants by PCR and Southern blotting showed that the selectable marker gene hph was integrated effectively into the genome of Valsa mali var. mali.After 5 subculturing on PDA,87. 5% transformants could grow. This stability test of transformants suggested that the foreign gene hph was stable in heredity.[Conclusion]This transformation system is a valuable and important tool for the further study of the pathogenic gene of Valsa mali.