Olfaction plays an important role in the survival and reproduction of insects. In recent years, extensive studies have been conducted to reveal the molecular mechanism of olfactory sensation. Two major types of olfactory receptors, including odorant receptors and ionotropic receptors, play a vital role in the process of odor reception. To get a comprehensive view of the function of olfactory receptors, we summarized the discovery process, structural features, expression, and localization of odorant receptors and ionotropic receptors in this review, with an emphasis on the function and research methods. This review aims to provide implications for future functional studies of olfactory receptors and ethological dissection of insect behavior.