Abstract: In order to elucidate the relationship between the occurrence of insect pests and the CO₂ volume fraction in grain storage environment, the change of CO₂ volume fraction in stored wheat with different moisture contents and infested by different initial population density (0, 2, 5, 10, 20, and 30 adults per kg of wheat) was investigated. The results showed that the CO₂ volume fraction significantly increased with the increasing insect densities and treatment time in the wheat storage with the same moisture content. For wheat with a moisture content of 12% and initial population density of 30 T. castaneum adults per kg of wheat, the CO₂ volume fraction in the wheat storage environment was 1.383%, then reached maximum (13.187%) on the 30th day. For wheat with 14% moisture content and initial population density of 30 T. castaneum adults per kg of wheat, the CO₂ volume fraction in the stored wheat environment was 0.920%, then reached maximum 18.217% on the 24th day. The results provided reliable information for monitoring the occurrence of insects in stored grain by detecting the change of CO₂ volume fraction in the future.