Abstract: The tailings dam-break seriously threaten the downstream personnel life and property，and also environmental security. It is difficult to descript the problem accurately and quantitatively. The Bingham model，one of a non-newtonian fluid model，is adopted in this paper. Sand flow evolution process after a tailings dam-break in Liaoning is transient simulation analysis by using fluid dynamics analysis software ANSYS CFX. The flow regime change，velocity vector change and final accumulation form after dam-break are emphasized. The analysis results show that tail sand flow move to downriver by gravity after the tailings dam-break. A surge wave was formed when rushed out early stage，and spread to the downstream gradually. The tailings velocity of any time presents a gradual change，the tailings velocity increases gradually from the tip to end，and ground speed is faster than surface. Finally an accumulation body is formed，that its tail is thick and thin to the edge. The results will provide important basis to the formation of dam failure disaster emergency plan，the proposition of downstream personnel safety evacuation plan and hazard assessment after dam-break.

Key words: Tailings dam, Dam break, Numerical simulation, Accumulation body