During the electromagnetic launch process, the temperature of the rail is affected by many factors and it is difficult to analyze some factors accurately. Based on this, the gray system was used to study the temperature of the electromagnetic launcher. In order to obtain the experimental data needed for the gray model, the electromagnetic launcher data collection system was built, and such data as the current, the rail temperature, the launch speed and other factors concerned were collected. Due to the limitations of measuring instruments, the ANSYS finite-element simulation was adopted to correct the measured rail temperature data to obtain the inner surface temperature of the rail. Based on the classical GM(1,N) and Simpson formula, an improved gray model was proposed, and the rail temperature was studied by this method. The same energy level test was conducted to discuss the contribution of temperature rise of various factors at different locations. The conclusion provides a reference and basis for further research on the temperature of the rail.