The phosphine LC 50 of 11 strains in 5 species of stored grain insects,Sitophilus oryzae (Linnaeus),S.zeamais Motschulsky,Rhyzopertha
dominica (Fabricius),Tribolium castaneum (Herbst) and
Oryzaephilus Surinamensis (Linnaeus) were detected thrugh the method recommended by (FAO).The values of LC 50 of LS 2 and GDSo strains of S.oryzae,HNZZSz-1 and GDGZSz-1 strains of S.zeamais,QQRd and Rd-7 strains of R.dominica,QQTc-4,SDQHTc-1 and HNSQTc-1 strains of T.castaneum,and VOs48 and HNNYOs-1 strains of O.surinamensis were 0.0088 and 1.3006,0.0057 and 0.0058,0.0042 and 1.3779,0.0047,2.1009 and 0.9926,0.0073 and 0.0090(mg/L) respectively.LS2,HNZZSz-1,GDGZSz-1,QQRd,QQTc-4,VOs48 and HNNYOs-1 were susceptible strains.GDSo,Rd-7,SDQHTc-1 and HNSQTc-1 were resistant strains to phosphine,and they had resistant factors of 148,327,449 and 212 times.The results showed that they had a serious resistance to phosphine,and the results provided baseline of phosphine resistance of these strains cultured in laboratory of Zhengzhou Institute of Technology for studying phosphine resistance further.