It has been well known that a large and varied microbial community inhabited in the insect gut. With the development of methodology, particularly 16s rDNA based molecular techniques, the composition and function of insect gut microbiota are being gradually manifested in recent years. Insect gut is a selective environment for microbial colonization. Gut microbes play important roles both in the insect nutrition and colonization resistance against invasion of exotic microbes. Furthermore, they are volved in multitrophic interactions between the host and other biological factors, and  also be able to nhance the host's immune response. During evolution, the mutualism between gut microbes and insect host has been established, and the gut microbes developed strategies adapting to the environment of the insect gut. Here we reviewed the advances of recent years in the symbiosis between gut microbiota and insects. The practical significance of researches on gut microbial ecology and the hot spots in the future were also discussed.