Abstract: Unlike humans, the insect olfactory mechanism has many important effects on insect behavior, including habitat choosing, food-hunting, gathering, tropism, reproduction, signal communication, etc. The research of the insect olfactory mechanism can interpret some common mechanism of smell happened and the connection between the smell activity with the whole life activities. Thus,it provides a scientific basis for the research of olfaction higher animals, particularly humans.In addition, using this kind of life activity characteristics of insect to control pest is also a kind of important means in Integrated pest management. In recent years, with the rapid development of the insect behavior, biochemistry, molecular biology and insect electrophysiology, many bioactive molecules and genes associated with olfaction were found, and they interpret the possible reaction mechanism of sense of smell at the molecular level. In this paper, the author summarized the progress on odorant recognition, odorant-receptor interaction at the molecular level and the mechanism of electrochemical signal transduction.What's more, the article introduces the process that the scent signals transform into electrical signal via the olfactory sensors, then encoded and integrated by insect antennal lobe, eventually passed to the forebrain, and the molecular components and physiological or biochemical reaction in the insect body throughout this process.