Abstract: The inhibition of carboxylesterase (CarE) and acetylcholinesterase (AChE) in booklices by dichlorvos,paraoxon,chlorpyrifos and carbosulfan was studied.The results of bioassay revealed that these insecticides showed strong inhibition to Liposcelis spp,and L.bostrychophila was less sensitive than L.entomophila.CarE of L.bostrychophila was more susceptible to inhibition than that of L.entomophila only to dichlorvos.For the AChE,the four inhibitors showed strong inhibition to both L.bostrychophila and L.entomophila and had similar susceptibility tendency with CarE;and inhibition kinetics also indicated the similar tendency.The inhibition pattern for two species was simply tested by PAGE and it was obvious that the endurance of two psocids to these insecticides has no direct relevence with the sensitivity of CarE and AChE.The further study should be done to realize the real mechanism of endurance.