[Objective] The formation mechanism of rainstorm-induced debris flow in Yushu Plateau of Qinghai Province is researched. Which was expected to provide a basis for the prevention and control of debris flow disaster and reduction of the risk mitigation. [Methods] Through field survey

Lalong debris flow of Chengduo County in Yushu state was selected as an example

and the stimulus factors and mechanism were analyzed. [Results] The main channel length of the debris flow is about 3 km

the catchment area is 5.25 km2

the longitudinal gradient is 212‰

and the height difference is about 600 m. The volume of the landslide of the source area is about 6.50×104 m3

the volume of the debris flow is about 8.5×104 m3; and the volume of the material in the channel is 2.0×104 m3. [Conclusion] The process of rainstorm-induced debris flow in the study area can be divided into 4 stages: landslide-source formation

particle material starting up

gully erosion and debris flow initiation.