The unique structure and physicochemical properties of insect intestines provide suitable conditions for colonization by various microorganisms, the community composition of which is closely related to the growth, development, metabolism, reproduction and other life activities, of their insect hosts. Insects have an abundant and diverse gut microflora. The relatively stable symbiotic relationships between insects and their gut microflora play an extremely important role in the insect life cycle. Gut microbiota not only provide important nutrients for their insect hosts but also assist in the digestion of food, immune defense and detoxification. They also affect the life span, development, mating and reproductive capacity of insects. Insect gut microbes can potentially be utilized in many fields, including agriculture, ecology, medicine, energy and environmental protection. This paper reviews recent progress in research on insect gut microbiota, including its diversity, function, factors that affect it and its potential utilization.