As an important component of the infrared detector assembly, the fixing method of the linear motor of the Stirling refrigerator is an important factor affecting the reliability of the assembly. If the destructive force of the magnetic steel fixing is higher than 10 kN, the risk of the magnetic steel falling off will be reduced. Therefore, the destructive force of the linear motor of the Stirling refrigerator under different magnetic steel fixing methods is studied. The test results show that in the case of pure gluing or pure welding, the maximum destructive force when the glue is fully applied and one-circle welding is used is close (about 6 kN), and there is a risk of magnetic steel falling off. In the case of combining the two methods, the destructive force when the glue is fully applied and the 6-point welding is used is 11.18 kN, which meets the requirements of magnetic steel fixing; the destructive force when one-circle welding is used is 17.02 kN, which greatly increases the reliability. The simulation data is close to the experimental results, which proves that when the glue is fully applied, the minimum welding condition to avoid the magnetic steel falling off is 6-point welding. When the welding points are less than 6, there is a risk of magnetic steel falling off, causing the refrigerator to hit the cylinder and make an abnormal noise. This result provides a reference for the reliability design of subsequent refrigerators.