Abstract: Forecast of the discharge process of dam break flood routing to the downsrteam section is extremely important for scientifically response to flood disasters such as barrier lake or dam break.In view of the dam break flood characteristics of Unsteady Rapidly Varied Flow,the dynamic coordinate method of discontinuous wave is used to transform the unstready flow issure of dam break flood routing into stready flow issue.The calculation of dam break flood and routing to downstream section applied the microelement method to put foward a dam-break flood routing analysis model based on dicontinuous wave,which is verified by the"10·11" Baige barrier lake breach flood routing.The results show that the measured peak discharge of Baige barrier lake breach flood in Yebatan Hydropower Station,which routed to Suwalong Hydropower Station just has an error of 1.44% with the time is 10 min ahead,the peak discharge error of the flood routing to Benzilan,Shigu and Liyuan hydropower stations are around 10%.The feasibility and rationality of the model are verified.This work also demonstrated the efficiency and stability of the discontinuous wave flood routing model,it can effectively support emergency disposal decisions.