Abstract: For discontinuous high index differential-algebraic models(DAE) from performance simulation of physical systems,an index transformation method based on weighted bipartite graph is proposed.By representing a DAE system as a weighted bipartite graph,the proposed method can determine if the DAE system is high index by a bipartite graph matching algorithm,and for a high index DAE system,the method can locate minimal structurally singular subsets of equations which need to be differentiated in order to transform the high index DAE system into a lower index formulation.Based on the proposed method,the strategies for index analysis of discontinuous DAE models are presented.The proposed strategies and algorithms have been successfully implemented in a Modelica based modeling and simulation system,named MWorks.