In order to study the mechanical properties and microscopic mechanism changes of microcrack propagation of FeNiCu alloy at different temperatures. In this paper, molecular dynamics methods were used to simulate uniaxial tensiles of FeNiCu alloy models containing microcracks and dislocations at 300, 500, 700, 900 K and 1 100 K, respectively. The microstructure evolution of FeNiCu alloys during tensile process was analyzed using Visualization software. Combined with the stress?strain curve and the energy change curve, the micro?mechanism effect of temperature on micro?crack propagation of FeNiCu alloy was emphatically analyzed. The results show that the higher the temperature in these five sets of temperatures, the greater the atomic spacing in the alloy and the more unstable the microstructure. However, the increase in temperature improves the plasticity of the alloy, so that the microscopic defects within it are healed to a certain extent under uniaxial loading, and the mechanical properties are maintained relatively stable. In addition, when the temperature rises, dissociative slip will be strengthened, which aggravates the emission and motion of the dislocation, and the dislocation product will be more likely to form microcracks, so that the dislocation <110> will form microcracks in multiple places in the slip direction.