Leaky-wave antennas (LWAs) are well-known for the high directivity, wide impedance bandwidth, and the beam-scanning performance with frequency. However, in the system that requires high-speed data transfer, wide system band and high directivity, LWAs are struggling with their beam squint effect in the radiation patterns, which limits their applications. In this paper, a dispersive metasurface prism is loaded to a dispersive LWA, reducing the LWA's dispersion, to make the LWA wide band radiating at a specific direction. A substrate integrated waveguide (SIW) LWA is taken to demonstrate the proposed concept with metasurface prism implemented by metallic vias. Full-wave simulation results show that the proposed low-dispersive SIW LWA has the main radiating direction at φ=24°, with half-power beamwidth of 8°, steers only ±0.5° from 33 to 38 GHz.