Abstract: Using the HPLC analysis technique, the contents of autotoxic substances（cinnamic acid and vanillin）in eggplant replanting soil were determined, and the effects of grafting on eggplant growth and soil biochemical properties under the two autotoxic substances stress were studied in a pot culture experiment. The results showed that cinnamic acid and vanillin existed in soil of eggplant continuous cropping. The contents of cinnamic acid and vanillin in soil increased with increasing planting years, the content of cinnamic acid ranged from 17.08% to 27.09% of vanillin. Grafting could improve the adverse effect on eggplant growth and soil biochemical properties under the two substances’ stress. Under cinnamic acid and vanillin stress, own-rooted eggplant growth was inhibited, whereas grafted eggplant growth was slightly promoted. Compared with own-rooted eggplants, grafted eggplants rhizospheric effect（R/S）of bacterium and actinomyces increased, whereas R/S of fungi decreased, with R/S of actinomyces reached the maximum 2.92 under 4.0 mmol · L-1 cinnamic acid, that of fungi reduced to minimum 0.61 at4.0 mmol · L-1 vanillin；The R/S of saccharase, urease, phosphatase of grafted eggplant soil increased with increasing concentration of cinnamic acid and vanillin, and R/S of saccharase reached to the maximum 2.32 at 1.0 mmol · L-1 vanillin.

Key words: cinnamic acid, vanillin, grafting, eggplant growth, soil biochemical properties, rhizospheric effect（R/S）