To shorten the research and development period and to lower the complex of design of cold spray system, a commercial software Star-CCM+(Version 6.04) is used to calculate the state of gas flow, the relationship between exit temperature and the structure of gas heater, flow rate and heat input. The results indicate that a steady temperature can be reached for the whole gas heater. The velocity of the gas changes little in the tube. There exists a large temperature difference between resistance tube and the gas. An optimized heater structure can increase the efficiency of heat exchanging. To ensure a high efficiency, the length of the resistance tube must be long enough; the larger the center pitch, the higher the exchange efficiency. The suitable diameter (8-12 mm) is also required for the resistance tube.