Chlorpyrifos is an organophosphate pesticide that acts as an insecticide-acaricide by ingestion, contact, and inhalation, and is now widely used in greenhouse for the control of pests. The dissipation of chlorpyrifos in crops such as orange fruit （Martinez-Vidal et al., 1998）, tomatoes（Aysal et al., 1999）, soil and its effects on soil microbial characteristics （Singh et al., 2002） has been reported frequently. However, little information is available to describe impacts of chlorpyrifos on soil microbial population and enzyme activity in greenhouse. In this study, the effect of chlorpyrifos on soil bacteria, fungi, actinomycetes, and soil enzyme activity was investigated.
