The failure of a die casting fixed core was described, such as ablation, crack and aluminization, and the causes of the failure was analyzed. Mould repair was divided into marking, welding, digital control milling and electrical discharge machining processes, and the quality of the repaired mould could meet the technical requirements. Meanwhile, the measures to improve the service life of die casting mould were discussed, including reasonable structure design of die casting mould, proper choice of die material, optimization of heat treatment process, proper operating environment and standard maintenance.