At present laser thermo-repairing for the defects on gray cast iron surface is becoming an important way of casting equipment cycle remanufacturing. A reliable numerical model for the repair process is established, where the heat source expression and boundary conditions are refined. Then the model is verified by experimental results to achieve higher precision. The calculation results show that the secondary repair is processed in a warm-up state. Compared to single repair, multilayer repair can provide more methods to control temperature cycle curve. In the material fused circulation on matrix surface, the materials are compressed at first and stretched then in length and width direction. Compression stress is given priority in the repair stage, and when materials in thickness direction are under alternating tensile-pressure stress cycle, tension is given priority. Stress becomes more focused in the U trough bottom than its sides.