| After more than 20 years large-scale forest closing in the upper reaches of watershed of Miyun reservoir, the restoration of vegetation has received expected effects in hilly area, low mountain and middle mountain. However, there remain a large number of low quality and benefit secondary forest. It is difficult to achieve the desired effect of water conservation and accumulation is low. Therefore, it is imperative to make the forest conservation efficient through orientation regeneration and succession.Based on investigation of the vegetation in watershed of Miyun reservoir, it used the GIS data of the secondary forest resources inventory to analyze the present characteristics of water conservation forest. It made distribution trends of different dominant tree species at different elevation, slope, aspect, soil thickness. According to the principle of the key factors and the principle of practicality, we classified Miyun to 3 site-type small-districts,9 site-type groups and 15 site-types and made the graph of the site type Miyun by using GIS. Through the classified site type, we calculate that the accumulation potential of the water conservation forest in watershed of Miyun reservoir is 2.3×107 m3 which can provide guidance for production.In order to determine idea area and percentage of different tree species in Miyun, the structure of the water conservation forest was adjusted by using AHP. The adjusted area were mixed forest> broadleaf forest> coniferous forest> shrub forest and the corresponding area were 54571.5 hm2, 33960.8 hm2,20025.2 hm2,8548.8 hm2.In the process of improving low quality and benefit forests, reconstruction model and goal indicators of forests in different site types were proposed. In addition, we proposed a low-intensity and time and space crisscrossing method which can play the role of reducing soil erosion and water conservation.
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