Abstract: Sealant is an important component of aircraft structures and the basic guarantee of structural seal safety. If the performance parameters of sealant are not up to standard, it’s impossible to achieve the design goal. A new HM109 modified polysulfide sealant was tested and analyzed, and simulation calculation was carried out by finite element simulation software, with Cohesive element used to simulate the sealant layer. By observing the failure process of the sealant layer, the failure process of the sealant layer of aircraft seal structure under heavy load was determined. The reliability of finite element simulation analysis was verified by comparing the test results with the simulation results. The results show that the measured parameters are applied to the finite element simulation, and the simulation results are basically consistent with the test results. The error between the simulated results and the average test results is about 3.74% and 1.5%, and the simulation results are reliable.