Abstract: The susceptibility of five populations of Hylyphantes graminicola collected from different habitats in Wuhan,China,to fenvalerate,deltamathrin and fenvalerate were investigated by dipping methods. The results showed that H.graminicola from different habitats had different sensitivity level to pyrethroids.H.graminicola from grass field was the most sensitive population to the 3 pyrethroids,and that from cotton field developed middle level of resistance to fenvalerate and the relative resistant index was 14.61.Biochemical study showed that the activities of esterase,MFO-O-demethylation and GST of the grass field population were the lowest,while the activities of esterase and MFO-O-demethylation of the cotton field population were the highest.It was suggested that the resistance of H.graminicola to pyrethroids may be related to the increased activities of esterase and MFO-O-demethylation.