Abstract: Forest gap was a smallscale forest disturbance occurring commonly, which played a very important role in sustaining forest regeneration and cyclic succession. Based on previous related literatures, how the forest gap formed and the external characteristics of the forest gap were systematically elaborated, and the differences among microenvironment forests disturbed by forest gap, such as illumination intensity, the air temperature and humidity, physical and chemical properties of soil, and so on, were summarized. The size, shape and border tree characteristic of forest gap was the direct factors explaining environmental heterogeneity. The article, based on disturbance theory and regeneration theory, analyzed the impacts imposed by gap disturbance, seed dispersal, species diversity and plant regeneration and growth, etc. In the end of this paper, it put forward the near future development direction and gave us a practical guide on forest tending with the theory of forest gap.