Abstract: Biodiversity security is one of the main watershed ecological security and study hotspots in the recent years. Based on the ecological security landscape theory and remote sensing and GIS spatial analysis techniques，this paper put out the four periods of ecological security landscape of area in the Yongding River watershed from 1984 to 2010 at the regional level. By defining the value of the pixel resistance （expense），the paper graded the ecological security level，analyzed and compared this area ecological security situation in the different periods and the spatial-temporal changes. The results indicated that the constructed regional-scale ecological security landscape can express the state of the regional-scale ecological security pattern；the proportion of low-security area in Mentougou Basin，Beijing，decreased from 9.49% in 1984 to 9.18% in 2010，the ecological safety state of the western mountains of the study area is better than that of the eastern plain. According to the results, areas of low ecological security should be given priority for the protection and ecological restoration.

Key words: effective cost distance model, landscape ecological security pattern, GIS, the Mentougou basin