In order to study the projection angles in asymmetrical structure, the oblique shock wave theory was used to describe the process of detonation wave shocking on the metal surface. The calculation method of projection angle was obtained after the velocity multiplication law on free surface simplified the shock wave theory to estimate the velocity of particles in metal. The explosion experiments of a D-shaped warhead were done to validate this method. The results show that this method is in good agreement with experimental data; when the incident angle is less than 40°, the projection angle will increase linearly with increasing the incident angle.