Abstract: The 5 instar larvae of susceptible and resistant populations of cotton bollworm Helicoverpa armigera (Hübner) were treated with fenvalerate, methomyl, parathion methyl and endosulfan at the LD 50 and LD 95 dosages. The effects of 4 insecticides on respiratory metabolism to 5 instar larvae were measured. The results showed that although the dosages at the LD 50 of fenvalerate and methomyl to R population were 15.8 and 14.1 fold higher than that of S population, but the respiratory inhibitory rate of R population were lower than S population.The respiratory inhibitory rates of parathion methyl and endosulfan at LD 50 dosages to R population were lower than that S population after treating 300～1440 min. At the LD 95 dosages, the respiratory inhibotory rates of fenvalerate and parathion methyl to R population were 14.7%～27.3% and 27.2%～15.5%,to S population were 42.0%～48.6% and 45.8%～50.4%. It showed that the endurance abilities of R population to insecticides and respiratory metabolism were higher than that of S population.