Based on irradiation hardening theory and crystal plasticity theory, tensile process of irradiated polycrystalline copper was simulated with ABAQUS finite element analysis software. Effects of irradiation on mechanical properties of materials such as yield strength, hardening process, crystal deformation are analyzed. Temporal evolution and spatial distribution of dislocation density are studied. It shows that: The yield stress of polycrystalline copper is increased with irradiation and hardening and softening phenomena in different stages are affected. The increase of irradiation dose slows the proliferation of dislocation density, and increases its spatial inhomogeneity. Plastic deformation and crystal rotation are also affected by irradiation. Under same strain condition, the greater the irradiation dose is, the greater the deformation degree is and the greater the inhomogeneity of plastic deformation distribution is. Meanwhile, with the increase of irradiation dose, the degree of crystal rotation and angular dispersion increases.