Pot experiments were carried out to study alleviation effects to autotoxicity of attapulgite clay in pepper. Peppers were planted in pots of DBP-contaminated soil, 80 mg/kg in DBP concentration, and different addition of attapulgite clay. Effects of attapulgite clay were studied on pepper growth and physiological and biochemical indexes. The results showed that DBP had a significant autotoxicity to the growth and physiology metabolism of pepper. And attapulgite clay could alleviate the DBP auto-toxicity in pepper. When the dose of attapulgite clay was 20 g/kg in soil, the pepper had the minimum in MDA content and the maximum in POD activity, CAT activity. At the same time, root activity and respiratory rate were in strongest, root absorption areas in biggest that including the total absorption area, active absorption area and specific surface area, and chlorophyll content in highest. The above meant the alleviative effect on autotoxicity of DBP was best for attapulgite clay with the content of 20 g/kg in soil. However, when the dose of attapulgite clay was 80 g/kg, the plant growth and physiology metabolism would be decreased obviously, and the alleviation effect of attapulgite clay on DBP would be weakened or disappeared. So it was suggested that the optimum was 20?– 40 g/kg attapulgite clay.