Abstract: In this study， pepper variety 8819 were used as the material， and spent substrates were used as the organic fertilizer， the effect of five different dosages of spent substrate on pepper variety 8819 were exhibited on plant height， stem diameter， soil microorganism, protective enzymes and the content of chlorophyll and malonaldehyde. The results showed that when compared with the control， application of different dosages of spent substrate promoted pepper growth， especially increased the stem diameter， and got the largest stem diameter at the dosage of 800 kg·667 m-2. The effects of different dosages of spent substrate on the content of chlorophyll in different growth stages of pepper were different. All the treatments increased the content of chlorophyll significantly in the whole growth and development stages of pepper， the chlorophyll content of treatment B could be increased by 10%-292% than other treatments. The application of spent substrate increasd the quantity of soil bacteria， actinomycetes and fungi， and could improve the soil fertility， thus contributing to the growth of pepper. The effects of different dosages of spent substrate on protective enzyme system showed that the activities of POD and CAT were decreased in all treatments. However， it is no linear to the degree of decline and in the dosages of spent substrate. All the treatment except A could decrease the content of MDA content significantly. Optimum dosages of spent substrate from 400 kg·667 m-2 to 1 600 kg·667 m-2 improved the photosynthesis of pepper and then improve the stress resistance. From all the results， it illustrated that application of spent substrate at dosage of 800 kg·667 m-2 is optimum in cultivation.

Key words: spent substrate, pepper, chlorophyll, soil microbial , catalase, peroxidase；malonaldehyde