The missile-borne test device often fails to work in the process of high-speed penetration of projectile into hard target because of the high overload. In order to ensure the viability of the test device in the high overload environment, the test device is buffered and isolated by the thin-walled metal tube and air gun test was carried out in this paper. The buffering efficiency of thin-walled metal tube is judged by four indexes, such as the separation efficiency, the volume specific energy absorption, the mass ratio energy absorption, and the load efficiency. The results show that the thin-walled metal tube with cone angle of 15 degrees has the best buffering properties.