Objective This paper furnishes a simulation tool for blood flow in the branch and network of blood vessel. It supplies references for fundamental research and clinic application. Methods Finite-element model and JAVA language are used to compile computer program of simulating blood flow in the branch and reticulated blood vessel. Results The program can construct vessel model, input blood vessel parameters and deal boundary condition. Computer data can be presented by output directly and figure display. The results are verified. Conclusion The method can conveniently build and modify model to simulate cardiovascular abnormalities, such as hypotension, hypertension, stenoses and haemorrhage.