Abstract: The biological activities of two IGRs,Methoprene and Pyriproxyfen,on Liposcelis entomophila (Enderlein),a main insect pest occurring in the preserver,were investigated systematically.By infiltrating two IGRs into the fodder,the different treatments and replication were set up based on the lethal effect of these two IGRs at different concentrations as well as the influence on development time and survivorship of L.entomophila nymphs.The results showed that two IGRs had obvious lethal effect on nymph,and the lethal effect of Pyriproxyfen on nymph was better than that of Methoprene.The development of L.entomophila nymph was delayed when insects fed on the food treated with Pyriproxyfen.These two IGRs had no acute lethal effect on adult;however,the adult fecundity was in hibited significantly.The inhibition of Methoprene on adult fecundity was 5 times greater than Pyriproxyfen.In addition,these two IGRs had obvious lethal effects on egg hatching,whereas the effect of Pyriproxyfen on egg hatching was greater than Methoprene.