A highly sensitive olfactory system can help insects accurately identify different volatile compounds and play a vital role in activities such as foraging, mating and oviposition. Insects use a huge number and variety of olfactory receptors on sensory neuron membranes to recognize different odors and regulate their behavior. Three main families of insect olfactory receptors have been identified: ionotropic receptors, odorant receptors, and gustatory receptors that respond to carbon dioxide and pheromones. At present, the molecular structure of olfactory receptors and the signal transduction mechanisms mediated by olfactory receptors have not been fully elucidated, also the identification of olfactory receptor ligands needs further research. In this review, we summarize progress in research on the structure, evolution, and functional characterization of insect olfactory receptors, as well as the mechanism of odorant receptor-mediated signal transduction, in order to provide some theoretical references for studying insect olfactory coding and regulation, as well as the interaction between insects and plants.