Abstract: Reliability of brazing process in ceramic package manufacturing depends on the interaction between thermal stress induced by mismatch of CTE(coefficient of thermal expansion) and defect in ceramic generated in the process before brazing. This paper based on the feature that defects with different degrees of danger spatially locate differently, and employed ANSYS software to analyze the distribution of the thermal stress in brazing process. A novel idea of avoiding the stress locating at defect region was applied to improve the reliability of assembly process. This idea is different from the traditional optimizing method to lowering the stress over the whole component, and is more flexible for the package design, and it is also more effective for improving the reliability of ceramic package manufacturing.