An incubation experiment designed by second-order regression orthogonal rotation was conducted to study soil microbial activities and functional diversity of microbial community in red earths polluted by copper,zinc,lead and cadmium compound state.The results showed that soil microbial activities and functional diversity of microbial community were inhibited very significantly or significantly by heavy metals compound pollution.Moreover,soil microbial biomass carbon(SMBC),soil basal respiration and functional diversity of microbial community are very sensitive to the level of heavy metals pollution.At the same lime,the relative biological toxicity of heavy metals to soil microbial parameters were in the order:cadmium>copper>zinc>lead.The results of canonical correlation analysis showed that the first(r=0.885 8)and second(r=0.932 8) canonical correlation coefficients were significant,which suggested that there exists a stable feed-back mechanism between soil mieroor-ganism and heavy metals contents in red earths.The main factors analysis opened out that the total microbial ecological index might be a useful parameter to assess changes in soil quality with management of these highly contaminated soils,So it is feasible to use soil total microbial parameters as primary biochemical index to evaluate the effect of heavy metals compound pollution tin red earth environmental quality.