Abstract: There is highly significant to estimate the ecological security of the forest landscape ecosystem in the upper reaches of Shiyang River basin which has become the typical ecological degeneration region in arid inland river basin in China recently. In the arid mountains area，the patches characteristics of wasteland can reflect the state of degeneration of vegetation，and the patches characteristic of farmland can reflect the threatening degree of natural vegetation damaged by farmland reclamation. So the magnitudes of potential risk of vegetation degeneration and the threatening degree of farmland reclamation of the forest landscape types should be indicated by analyzing spatial neighboring characteristics between these landscape types patches and the wasteland paths or farmland paths indirectly. In this paper，the ecological security of forest landscape ecosystem in Haxi forest area located in the upper reaches of Shiyang River basin was estimated by quantitatively analyzing neighboring characteristics between the forest landscape types patches and wasteland or farmland patches. With the support of GIS technology，and taking the Landsat/TM images and forest form map as the data source，the landscape types in study area were obtained by employing the artificial interpretation method. The forest landscape was classified into seven landscape types which was grassland，wasteland，farmland，Picea crassifollia forest ，Sabina prezewalskii forest，broad-leaf forest and shrubbery. Spatial analysis methods were used to calculate the spatial neighboring length and number between forest types and wasteland or farmland，and buffer zone analysis was used to calculate the areas influenced by wasteland and farmland. On this basis the threatening degree of mountain forest ecological security in the arid region was discussed. The results showed that shrub had most neighboring length and numbers with wasteland ，and grassland had the most proportion of neighboring length. It indicated that the shrub and grassland had more threats of vegetation degradation and fragmentation mainly caused by grazing than arbor forest. Picea crassifollia forest had most neighboring length and numbers with farmland，and broad-leaf forest had the most proportion of neighboring length and path numbers，proportion of neighboring length with farmland of Sabina prezewalskii forest was also higher than that of shrubbery and grassland. It indicated that arbor forest had more threats by clearing for agriculture than shrubbery and grassland. There were similar character in the influencing area by wasteland and farmland，the areas influenced by farmland of each arbor forest type were obviously larger than the area influenced by wasteland. The threatening degree values （C values） by wasteland of shrubbery and grassland were 0.89 and 0.81，relatively high，and that of arbor forest types were relatively low，with about 0.6. The C values by farmland of arbor forest types were obviously higher than that of shrubbery and grassland. The C values by farmland of broad-leaf，Picea crassifollia forest，Sabina prezewalskii forest，grassland and shrubbery were 2.26，1.1，0.78，0.47 and 0.25 respectively. On the scale of whole forest landscape，the threaten caused by wasteland was higher than that caused by farmland. The assessment of ecological security based on spatial analysis could reveal the threatening degree of mountain forest ecosystem in arid region by human activities.

Key words: Forest landscape, spatial neighboring, ecological safety, upper reaches of Shiyang River basin