Abstract: Lengdu complicated slope, located in the cross zone between Shuoduogang River and Jinshajiang River, the east of the first area of the reservoir of Tiger-leaping-gorge power station, and the large Jinshajiang bridge for Yunnan-Tibet railway, has been regarded as a large landslale. Based on field investigation and comprehensive analysis, the paper concludes that it was a large complicated slope caused by inner and extra geological process. The frontier part of slope is composed of loose deposit, existing local sliding phenomenon, the mid-part appears as broken mass caused by fault movement, the upper part is covered by scattered rock blocks. It is considered that the large slope is stable state in whole at present, However, it is possible that the fronter part of slope will failure after the reservoir inundation.