Abstract: The hazard of old accumulation of debris flow that occurred under the factors induced by engineering activities of human beings still hasn't aroused people's attention. The Bietuo old accumulation of debris flow where the Bietuo segment of west approach road of Erlang Tunnel on Sichuan-Tibet Highway is selected as a case to introduce it's evolution and it's fabric character, then analyze the mechanism of the geological hazards along the highway, and finally, generalize the hazard effect and the corresponding prevention and cure measure when taking activities of engineering on old accumulation of debris flow.