With the rapid development of the electronic packaging industry, the industry’s requirements for the reliability of packaging structures are becoming more and more stringent. At present, most people regard Poisson’s ratio as a fixed value, which will affect reliability prediction to a certain extent. In order to further improve the reliability, it is of important engineering practical significance to properly consider the influence of the material Poisson’s ratio on the package structure. This paper uses finite element method (FEM), through design chip simulation and board-level packaging simulation, to explore the effects of Poisson’s ratio of epoxy molding compound on the chip warpage, chip interface stress, and the impact of board-level packaging solder joint life. Through analysis, it can be known that the variable EMC Poisson’s ratio has a greater impact on the warpage of the package structure, and it may cause the chip interface to be delamination and the chip to reach the stress limit and damage. In addition, it is necessary to properly consider the influence of Poisson’s ratio on the fatigue life of solder joints. Especially with the continuous development of chips in the direction of large size, the study of material Poisson’s ratio will have more important significance.