This paper analyzed and calculated the impact of the Sanyanyu gully (Dayu gully and Xiaoyu gully) based on the collected data (debris flow dynamics important parameters). It was found that the impact force of the circulation zone is greater than that of the accumulation zone, the impact force of massive stones in the accumulation zone shows a trend to increase first, and then decrease. At last, the authors made a brief assessment on the calculated results according to the Liziyida debris flow gully, and proposed a specific advice on disaster prevention based on these studies.