The effect of pesticides on anaerobic microbial in purple paddy soil is usually used as an important guide line for estimating the ecological safety of soil. Effects of pesticide contamination on population and activity of bacteria were investigated in purple paddy soil by indoor culture method. The results showed that the population and activity of anaerobic fermentation bacteria and anaerobic nitrogen-fixing bacteria were stimulated slightly by adding carboforan or butachlor in paddy soil, but significantly inhibited by adding of butachlor (10 mg kg^-1), carboforan (10 mg kg^-1) and carbendazim (0.5 mg kg^-1). At the firstly week the inhibition reached the maximum and then gradually reduced down to the level in control. The same effect was found to the activities of urease and neutro-phosphatase by pesticides. The inhibition effects of the pesticide contaminants were gradually attenuating after forth weeks. Pesticide is an important factor affecting the soil microbial population and enzyme activity.