The work aims to solve the shortcomings of traditional rigid foam plastic fragile cover, such as insufficient pressure bearing capacity, unstable bursting performance, ineffective moisture and humidity control, and poor electromagnetic compatibility. The design of film cover was carried out with the sealing cover of the launch cylinder in a missile weapon system as the main application object, including overall structural design, component design, functional design, and simulation verification. After performance evaluation, the sealing, pressure-bearing, bursting and electromagnetic compatibility of the film cover could meet the requirements of equipment storage and use. The maximum peak impact force breaking through the cover could be kept between 1 200 and 1 600 N. An integrated design method of the structure and function of the film cover is established, which can meet the design requirements of the new type of sealing cover for the model under study and provide technical reserves for the smooth development of the large-size sealing cover for the new type of missile launcher.