Based on a comprehensive review of previous researches on ecological disturbance degree,this study aimed at watershed-scale landscape pattern on the Loess Plateau in West Shanxi Province.Watershed landscape naturalness(WLN),a new index,was introduced to describe landscape pattern characteristics,and its spatial expression on map and the methods of quantitative analysis were developed as well.Landscape of Caijiachuan watershed is composed of woodland and the patch mosaics of shrub-land,wasteland,and cropland.In the watershed,the middle part shows the highest degree of patch fragmentation,most significant heterogeneity,obvious edge-effects,and relatively even distribution of all types of patches.In the lower part,although patch fragmentation decreases,the area of natural landscape types is reduced and meanwhile the area of artificial landscape types increases.The slight edge-effects in the upper part of the watershed indicate favorable habitat and high biodiversity.From the upper to the lower part of the watershed,the ecological disturbance degree caused mainly by human activities increases and the WLN decreases gradually,while semi-natural landscape and man-made landscape show an increased trend.