Abstract: Apple fruit(cv. Golden delicious)was used as material to study the effect of different concentrations of chitosan combined with 50 μL/L polylysine dipping on blue mould and partial mechanisms. The results indicated that 1.0% chitosan combined with polylysine treatment significantly decreased lesion development on apple fruit inoculated with Penicillium expansum,and also increased the activities of phenylalanine ammonia lyase(PAL)and peroxidase(POD),the contents of total phenolic compounds,flavonoids and lignin in the fruit. Chitosan combined with polylysine treatment also increased the activities of catalase(CAT),ascorbate peroxidase(APX),glutathione reductase(GR)and the content of hydrogen peroxide. These results suggest that chitosan combined with polylysine treatment decrease blue mould of apple fruit was closely related to enhancing anti-oxidative ability and accumulation of secondary metabolisms.