Abstract: Finite element characteristics split (CBS) algorithm was used to solve the equation of two dimensional shallow flow and a mathematical model for simulating the sediment transport under dam-break flow was established. CBS algorithm has good stability and accuracy in solving convection dominated problems, which can be applied to dam break flow that is characterized as large velocity, rapid change of water level and river bed. The validity of the model was verified by comparison of the calculated result with the experiment data of a full dam break flow in 90° sharp flume. On this basis, the model was further used to calculate flood routing and sediment transport under dam break flow field in 180° sharp bend at gentle slope and steep slope respectively. The results show that the model can simulate the dam break flow movement, and the results comply with the laws of flow and sediment movement.