When a high-speed vehicle (HSV) is under emergencies such as instability, out of control, etc., a space TT&C system may face the problem that TT&C antennas in ground stations cannot continuously track and align the HSV, which causes the interruption of TT&C communication links and finally fails to transmit safety-control command and telecommand. In order to maintain TT&C communication links with ground stations when a HSV is instability, out of control, and non-line-of-sight (NLOS) propagation, it is proposed to apply shortwave communications to HSV TT&C system as an emergency communication method. Therefore, a flight experiment of NLOS shortwave propagation was conducted on a HSV. In the experiment, a ground station emits shortwave at 7 MHz, and the shortwave signal is received by a magnetic field meter that is installed inside the HSV. The magnetic field intensity of the received shortwave and background noise in fight environment are obtained. The experimental results show that as the altitude of the HSV increases, the magnetic field intensity decreases, and the HSV can always receive the shortwave signal in the case of NLOS and of antenna misalignment, which experimentally verified the viability of this method. This is the technical base of maintaining communications of HSV in long distance, beyond the horizon, and denied environments, and also provides important data to develop shortwave emergency communication systems for HSVs.