To evaluate the working state after turning off some valves in an urban water distribution system(WDS) when there was a pipeline breakage,this paper established a failure consequence evaluation model,in which the node demands decrease of affected pipelines,the node demands decrease and the pressure reduction of non-affected pipelines were taken as three estimate indexes.And because all the variables were the node’s properties,their values were easier to get from the hydraulic model.As a basis for the model,a micro-hydraulic model named water supply pipeline failure hydraulic model was established.It redistributed node demands firstly,and then automatically adjusted the node demands under node pressure,and was calculated by genetic algorithm(GA).By the simulation experiments in a small water distribution system,it showed that the assessment model worked well.According to the results,the reasonableness of the valve’s arrangement and the role of some pipelines in the network can be effectively analyzed.