Abstract: The degradation of fipronil in soils was studied under laboratory conditions.Three kinds of soil,including (namely) black soil from Northeast of China,red soil from Jiangxi Province of China and rice soil from Jiangsu Province of China,were used in the research.Results indicated that fipronil degraded slowly in these soils.The half-life of fipronil under aerobic condition were 165 d,267 d and 42 d in black soil,red soil and rice soil,respectively.The half-life of fipronil under anaerobic condition was 31 d,173 d and 32 d in black soil,red soil and rice soil,respectively.Fipronil degraded fast in rice soil in both conditions.It's deduced that the bio-degradation of fipronil in these soils played a main role.As the degradation of fipronil was accelerated under anaerobic condition,it was supposed that anaerobic bacteria in soil may be the key factor in fipronil degradation.