Abstract: Frequent mining activities and discharge of waste residues in the Xiaoqinling gold mine area have led to serious hidden dangers of slag-debris flow. A heavy downpour hit and aroused a debris flow in Haocha Gully on July 23, 2010, which caused death of eight persons and ruin of houses and storages. Profile research on initiating and circulation areas gave the parameters of turning radius, discharge section, water level, bed slope and denudation degree. Grain size distribution of eluvium and residues was determined via samples in accumulation areas. Velocity and quantity of debris flow in different sections were calculated, and gully denudation and deposit volume were comparatively studied so as to estimate peak flow as well as theoretical and actual rainfalls. Based on the data obtained, the authors inverted the motivating factors and structure of the debris flow so as to provide basis for the early warning system of slag-debris flow.