A beam seal with an elliptical groove is proposed and parameterized. Based on the stochastic grid percolation model, macroscopic and microscopic finite element analysis, a sealing performance index is developed for the beam seal, which can consider the contact bandwidth and contact pressure synthetically. Taking the sealing performance index as the objective function, the sensitivity analysis of six main structural parameters of the beam seal is carried out by using the orthogonal array method. The orthogonal experiment with six factors and two levels is used to examine the interaction between parameter. It is found that there are parameter interactions between the length of the long axis and the short axis of elliptical groove, between taper angle and inclined angle U-shaped section, and between nominal contact width of the first seal and long axis of the elliptical groove. Furthermore, the sensitivity of each parameter on the sealing performance index of the beam seal is evaluated by the orthogonal design of L81(340) and F-test. The sensible parameters for sealing performance are obtained, and the optimal structural parameters of beam seal are suggested.