The outside heat-preventing coating of missile (rocket) often cracks, peels off and so on. In order to research the change of stress and strain of outside heat-preventing coating with different temperature, providing a reference for strength analysis, a 3D finite element model was established to study the change characteristics of stress and strain with different temperature. The result shows that the strain of coating will be negative value when the temperature increases, the maximum principal strain criterion should be used to judge whether the material is damaged. The strain of coating will be negative value when the temperature decreases, the Mises stress or maximum principal stress criterion should be used to judge whether the material is damaged.