Abstract: The service reliability of the laminar cooling structure directly affects the service safety of the engine. In this study, numerical simulation method was used to analyze the distribution of temperature and stress field in the laser welding process and service process of the typical closely spaced array hole column laminar cooling structure. According to the simulation results, the thermal fatigue life of the laminar cooling structure was evaluated by using the Morrow modified Coffin-Manson formula. The results show that the service state of the laminar passage area was little affected by the welding residual stress, but the service process has a great impact on it. The thermal stress amplitude in the laminar passage and nearby area reached the maximum, which was 1.6 times of the thermal stress amplitude in the weld area. It belongs to the dangerous area in the service process. It is estimated that the fatigue life here is greatly affected by thermal fatigue, which should be paid attention to in practical application.