In this study, laser sealing is selected as the sealing method for missile borne high-density T/R module. The energy distribution during laser sealing is described by finite element simulation, and the sealing test of T / R module is carried out. The finite element model of laser sealing of Si Al alloy is established. The stress field and temperature field of laser sealing welding of Si Al alloy are obtained by numerical calculation. Pulse laser welding can effectively control the welding line energy. There is a small welding stress in the welding center. The welding thermal stress of high silicon aluminum alloy packaging box increases obviously with the increase of the distance from the weld center. The highest welding stress of the shell appears at the side of the shell near the weld, and the maximum thermal stress is lower than the yield strength of the shell material. The welding parameters of laser seal welding are optimized. The welding peak power is 2.51 kW. The increase of pulse width has no obvious effect on improving air tightness. When the peak power is 2.51 kW, the requirement of air tightness of 2.14×10-8 Pa·m3/s can be met.