Based on the engineering project of jacket foundation of an offshore wind farm in the South China Sea after being hit by a transport ship, this paper analyzes the fatigue of jacket structure damage and strengthening. According to the S-N curve recommended in DNV GL specification combined with Miner's linear cumulative damage criterion, the fatigue calculation and analysis of jacket foundation node and impact area of jacket leg without grouting and jacket leg grouting were carried out respectively. The results show that after filling the jacket leg with high strength grouting material, the fatigue stresses concentration coefficient of the jacket jonits can be effectively reduced, the fatigue life can be improved. After grouting, the fatigue of the impact area and the fatigue resistance of the jacket tubular joints can be significantly improved. The high strength grouting material filling jacket leg programme has been successfully applied to the reinforcement of offshore jacket foundation in the South China Sea. This paper has certain reference value for the repairing of similar offshore wind turbine jacket foundation.