Abstract: To analyze the scale problem of surface defect of heat exchanger plate of PCHE, experimental analysis and research were carried out. The influence of surface defect width of plate on diffusion bonding performance of heat exchanger core mainly studied from two aspects of tensile strength and micro-interface structure. The results showed that when the defect depth was less than 0.1 mm and the width less than 0.82 mm, the surface defect had no influence on the weldability of the PCHE.