Abstract: In order to meet the requirement of welding quality of space pressure vessel and the protection requirements of special equipment inside, it is necessary to determine the welding specification by using the specimen before welding. The temperature field of TC4 titanium alloy pressure vessel specimen under certain process conditions was studied by using the rotating Gaussian surface heat source model. The distribution characteristics of temperature field and the thermal cycle curve of welding process were obtained, and it was proved that by using the distribution of the temperature gradient in the heat affected zone of the specimen provides the basis for the protection of the internal device. By simulating the evolution of the "key hole" and the characteristic dimensions at different welding speed, the welding parameters are analyzed and determined, it can provide a reference for obtaining high-quality requirement of the welding seam.