Abstract: [Objcctive] The paper aims to study whether the existing cotton varieties are resistant to Prodenia litura and Syllepta derogata Fabricius, find out what traits are related to the resistance.[Method] In the years of 2007, 2009 and 2010, Prodenia litura and Syllepta derogata Fabricius were serious occurrence, the natural occurrence of insect damage was observed in the field, and various agronomic characters of cotton were investigated. [Result] Different varieties had great differences in resistance to these two pests; It was found that Prodenia litura had no selectivity to Bt cotton, vigorous growth, stem and leaf with fuzzy hair were morphologic resistance to Prodenia litura, glandless cotton was damaged more. Bt cotton had better resistance to Syllepta derogate Fabricius; Population growing weak, cotton with thin stems were not resisted to Syllepta derogate Fabricius; Cotton with okra leaf or red leaf had better resistance to Syllepta derogate Fabricius. [Conclusion] Insect resistance is related to many characters, interaction between characters also plays a major role, the near isogenic line is the best material for the study of insect resistance.