The invention belongs to constraint methods and particularly relates to an axial vibration constraint method for a full-size warhead in a level situation. The axial vibration constraint method for the full-size warhead in the level situation is characterized in that an exciting device and a test piece are installed in a same level plane, the exciting device is fixedly connected with the test piece through a rigid connecting device, and movement of the test piece is limited in the output direction of the exciting device. The axial vibration constraint method for the full-size warhead in the level situation has the advantages that a hydrostatic bearing is adopted to conduct guiding and restraining, and meanwhile, the exciting direction passes through the barycenter of the test piece, crosslinking responses in other directions are effectively restrained, test conduction is facilitated, the effects of high safety and reliability are achieved, and the application range is wide.