Abstract: Taking tomato, biocontrol strains FC21 and tomato grey mould as test materials, the effects of different concentrations of fermentation broth FC21 on the germination rate of tomato seeds, the growth of tomato plants, the chlorophyll content of tomato leaves and the activities of resistance related enzymes and the control effect on grey mould of tomato were explored through pot and field experiments, in order to provide reference for the further development and utilization of FC21 against tomato gray mould.The results showed that compared with the control, the 100-fold dilution of biocontrol bacteria FC21 fermentation broth had the best promoting effect on the germination rate, bud length, root length and tomato plant, with the germination rate 93.18%,bud length 2.87 cm, root length 5.38 cm, plant height 21.32 cm and stem diameter 5.68 mm; the contents of chlorophyll a, chlorophyll b and total chlorophyll were the highest in 100-fold dilution treatment, which were 3.31 mg·g^-1,1.34 mg·g^-1 and 5.11 mg·g^-1;the activities of SOD,POD and CAT were the highest in 10-fold dilution treatment, which were 100.11 U·g^-1,128.36 U·g^-1·min^-1 and 13.96 U·g^-1·min^-1,and gradually decreased with the increase of dilution ratio.The control effect of 100 times diluted solution(1×10~6 cfu·mL^-1) on tomato gray mould was 73.46% in pot and 72.76% in field.The biocontrol strain FC21 had good control effect and growth promotion effect on tomato gray mould.