The invention relates to a multi-dimension coupling simulation method for irradiation damage of a nuclear reactor material. According to the method, by combining MD, KMC and CD methods, the respectiveadvantages are achieved, MD is used for simulating a cascade collision process, a simulation result is used as input of KMC, the KMC is used for simulating an annealing process of a cascade defect, asimulation result is used as input of CD, the CD is used for simulating a long-time evolution process of the cascade defect, large-space-time-dimension simulation from defect generation to microcosmic structure representation can be achieved, and accordingly material performance prediction under the service condition is achieved. According to the multi-dimension coupling simulation method, the limit of a single dimension is broken through, long-time and large-scale simulation from atom dimension defect generation of the irradiation damage of the nuclear reactor material to microcosmic structure representation is achieved, the irradiation damage mechanism of the nuclear material can be deeply known, and evolution of a microcosmic structure of an irradiation induction material is predicted.