Abstract: Such factors as overtopping，collapse，landslide and leakage occurred at dam body give rise to the failure of tailing dam.After failure，the tailing sand with high potential energy will form sand debris flow rushing to the downstream，which brings great risks on the safety of lives and properties of citizens living at downstream.Aiming at the outstanding problem of tailing dam accidents-dam failure，and taking Heyetang tailing pond in Baoshan as an example，the step-by-step simulation method was adopted to analyze the impact of 4# tailing dam failure on the safety of Maanling road at downstream by combining with the momentum process of migration and submerging of tailing debris flow，and the mechanical process of collision between debris flow and obstacles.After failure，the road submerging at downstream by tailing sands and the migration regularity of tailings debris flow directly influence the variation of disaster energy.So，the investigation on the collision between tailing debris flow and obstacles and the variation of energy can reveal the migration regulation so as to discover the submerged area of tailing debris flow at downstream，the migration regulation of tailing sand and the collision on highway at downstream and to discuss the safety of the highway.

Key words: Dam failure, Tailings dam, Debris of tailings, Submerged area