Abstract: For recent years, there were still some deficiencies in the ecological security research. For example, the spatial scales were not quite reasonably selected and the thresholds of ecological security ranks were determined with the lack of practical significance. And all these maybe decrease the credibility of research results. Therefore, for the current lacks of ecological security research, choosing the Guanzhong region with accelerating the urbanization process as study area which is located in Shaanxi Province, this paper built up the regional ecological security evaluation system on the basis of "pressure-status-response" model and gridding methods. In support of the gridding GIS technology, this paper gave each index in the evaluation system the spatial expression of 1 km?1 km grid scale. Subsequently, using the spatial overlaying technology based on grid data, this paper achieved the modeling evaluation of ecological security and acquired the gridding spatial data of every ecological security indexes for Guanzhong region in the year of 1990, 2000 and 2007. With the software of GIS, the paper carried out the spatial overlay analysis based on raster data and acquired the gridding data of ecological security of Guanzhong region. Combined with the reality of Guanzhong region, and referred to the current situation and circumstances of national forest parks and nature reserves, the paper tried to determine the threshold used to classify the ranks of ecological security by means of qualitative and quantitative methods. The results show that there are three features of ecological security of Guanzhong region. First , the ecological security of Guanzhong region is overall becoming better and better, but it is still unsafe; Second, the ecological security changes have the significant differences within the region. Third, there are different factors of affecting ecological security in different years.