On the basis of geological investigating work and experimental studies on slide zone soil of one landslide in Tibet��the authors analyzed granulometric composition��clay mineral composition and physical and mechanical properties for the soil in the slide zone�� The soil samples are gravel containing fine particle�� Particles larger than 2 mm occupy the main proportion with the content 51. 5%--68. 5%�� The relative content of clay minerals is low�� The clay minerals are illite smectite mixed layer and kaolinite��and their relative contents are 6% --13% and 4%-11%��respectively�� The main mineral ingredient is quartz and the relative content is over 30%�� Therefore��the soil’s hydrophily is poor�� The cohesion and internal friction angle are high��causing preferable physical-mechanical features of slide zone soil�� On the basis of the obtained data��the landslide stability is evaluated by means of limit equilibrium method�� The safety factors are 3. 191 and 1. 92 respectively under both natural and normal water level conditions�� The study results show that the landslide is stable�� It can provide the appropriate basis and reference for landslide stability evaluation and landslide control in Tibet��