Gaskets play important role in fuel stack assembly. It influences the assembly stress distribution or causes the risk of fuel leakage. The purpose of this paper is to study the assembly stress on the gasket and the MEA and the gasket development inside a stack of fuel cells. 2D and 3D models are established to explore the ideal behaviour of the couple MEA/gasket. A method is developed to define gasket shape parameters taking the MEA stress restrictions in consideration. Using PEMFC prototype, finite element simulations, pressure film experiments and joint integrity calculation code, an improvement on gasket section shape is performed to decrease the risk of fuel leakages. The design guideline and the analysis method proposed in this study will be helpful for the stack design to obtain high performance.