Abstract: The Botrytis cinerea hypha has been sonication with HEPES buffer (pH 8.0), and the crude protein solution was heated at 100 ℃ for 30 min, the protein solution filtrate was loaded on RESOURCE^TMQ 5 mL column at flow rate of 2 mL/min. Two peaks were collected, and the both peaks were analyzed by SDS-PAGE, and then the target protein (Botrytis cinerea activator protein) was detected hypersensitive response (HR) on tobacco leaves. Tomato seeds were subjected for a period of 45 days to 2.5, 5, 10 and 20 μg/mL of Botrytis cinerea activator protein (the molecular weight is16 kD) solution treatments, and 20 mmol/L HEPES buffer (pH 8.0) was used as control. Then inoculated by spray of 10⁵ cfu/mL the gray mold spore suspension and moisture 48 hours in incubator, and observed the morbidity at the 7, 14 and 21th days of inoculation; And sprayed 10 μg/mL protein solutions on tomato seedlings, then measured the phenylalanine ammonia-lyase (PAL), peroxidase (POD) and polyphenol oxidase (PPO) activities at 6, 12, 24, 48, 72 and 120 hours of treatment. The results showed that, the linear elution peak showing a single band with Coomassie Brilliant Blue R-250 staining, and this protein could induce the HR in plants. The disease resistance increased by 48%, 55% and 54% in seed treatment tomato respectively, and it showed most resistant at 10 μg/mL of the protein concentration. The PAL activity reached the peak value after 24 h of treatment, and it increased by 54% than that of the control. The activities of POD and PPO reached the peak value at 72 h of spray activator protein on tomato seedlings, and it increased by 106% and 122% than that of the control, respectively. Conclusion that, the activator protein involves the improvement disease-resistance by enhancement of the resistance-related enzyme activities in tomato, and the resistant effect was most efficient at the optimal concentration of the protein.