Based on the fork-shaped grating produced by the computer-generated hologram (CGH), the effect of the plane beam oblique incidence of fork-shaped grating on the vortex beams property is discussed. The theoretical study shows that when the plane beam tilts into the fork-shaped grating, the distance of each both symmetric distributed vortex beams is changed with the angle α between the planar optical and the grating. The experiments show that the distance of the symmetric distributed diffractive vortex beams spots increases with α. The research results show that the generation of high quality vortex beams is feasible with CGH in experiments.