Abstract: Pipes layout of nuclear power plant process system is significant phase of nuclear power plant design.Number of pipes in process system is huge and there are many constraints for the layout of these pipes.The design layout of the process pipes is easily affected by the plant structure and the change of equipment location.The traditional manual piping routing of process system in nuclear power plant has become one of the factors th at affect the design efficiency of nuclear power plant.Therefore,it is of great significance to work on automatic piping layout in nuclear power plant.Considering the plant size,radiation shielding and pipeline cost,according to the requirements of plant process piping layout,this paper adopted grid method to perform spatial dispersion and A^*（A-star）method to perform process system pipeline search according to the characteristics of plant design and equipment location.Automatic pipe routing of the pipeline in plant process system has been simulated based on this method.The design schemes which are the results of the automatic piping simulation code are accord with the requirement of process piping layout.It is verified that this method can be used in process piping layout of nuclear power plant.