RS/GIS/GPS is a series of efficient techniques for acquiring, managing and analyzing geographic information. This paper describes the using of these techniques in the Entironment investigation of Minjiang Upriver, based on national 863 projects 308 mission Xibujinjinxingdong sub-mission. With the help of forestry, water resource and agrology techniques, a main routine of work flow are introduced. It mainly comprises seven steps: (1) Collect related data, thematic maps, such as Land Use Maps and Forest Maps, were gathered; (2) Select the raw remote sensing images with thinking of the vegetation properties and the scale of target map. A red, green and blue (RGB) colors composite of Landsat TM’s band 432 is selected as the information sources;(3) Process and interpret the remote sensing images with ortho-image technique and interactive working method. As a result, 46 digital maps of 1:100,000 scale was produced;(4) perform field work or inspect on the spot with the help of GPS. More than 2000 kilometers routine and 294 patches was validated,;(5) Second time Interpretation;(6) Design and create the geodatabase. Not less than 20 layers was designed to contain necessary geo-information; and (7) Acquire, edit and store spatial data with the help of GIS software. After all these works, some spatial analysis is made. It clearly reveals large changes between 1990 and 2000: Nature forest area has decreased about 65000 ha; Manually planted forest has increased about 60000 ha; Grassland and plow land have been decreasing in various level; Arid valley has the tendency to enlarge. According to some forestry study, main reason such as over felling the forest, tillage on steep mountain slopes in upper river and government behavior is discussed to interpret these large changes in the end of this paper.