Abstract: The spatio-temporal distribution characteristics for main forest vegetation in terrain gradient was studied by using RS and GIS based on forest auxiliary graph, forest resource management inventory data, field investigation data. Two-temporal-satellite-images based on the ERDAS IMAGE 9.3 and ArcGIS 9.3,and vegetation mapping with the supplementary of forest distribution map of Argun National Natural Reserve from the year of 1992 to 2012 were interpreted. According to the analysis of TPI(topographic position index), the spatial distribution characteristics of main forest vegetation in terrain gradient were analyzed to explore the relationship between natural environment and human activities. The results showed that: coniferous, mixed broadleaf-conifer, broad-leaved forest and other forest vegetation occupied the dominate position of the land use pattern in whole study region, they located the early, medium and latter succession periods, respectively, and controlled process for the happens, development and ecological process of mountainous forest eco-system. The increasing areas of coniferous and decreasing areas of mixed broadleaf-conifer were very obvious, the transform from broadleaf-conifer to coniferous forest was the major conversation trace and very intensive of whole forest types. Additionally, the analysis results of terrain gradient showed: during the spatial distribution in area with terrain niche, the low and medium section zone was the dominate for coniferous forest, both mixed broadleaf-conifer forest and broadleaf forest mainly occupied the low section zone with terrain niche index from 1 to 5, the various extent of distribution index curve for coniferous, mixed broadleaf-conifer on terrain gradient was more distinct than that of coniferous, the distribution index for Betula platyphylla in two periods was very similar, the curve changed very obviously in terrain gradient and taken on the decreasing trend in whole level.