Abstract: In order to solve the high quantity of heat accumulation problems of the electromagnetic rail launcher, the rail cooling is necessary. This paper presents the basic principles for setting cooling pipes inside the rail from two aspects of mechanical performance and electrical performance analysis.An electromagnetic field and structure field model is established, the finite element method is used for numerical calculation of rail's response to the pre-tightening force and the eletromagnetic force. Simulation results show that, the cooling pipe will cause material damage, which has negative influence on rail performance; the cooling pipe should be set as far as possible away from the shoulder and armature-rail interface connection. This paper also puts forward the laws of rail deformation and inductance gradient with cooling pipe in different locations.