Vortex beams offer significant advantages for applications in optical communications, quantum information processing, and high-resolution imaging due to their capacity to support multiple information channels through varying topological charge modes. This paper presents the design and simulation of a terahertz metasurface that generates high-purity vortex beams with exceptional anti-diffraction properties. Traditional methods for generating vortex beams face challenges at terahertz frequencies, particularly concerning diffraction limits and efficiency. By optimizing the phase control of light using metasurfaces, we achieved the efficient generation of non-divergent terahertz vortex beams. The designed metasurface features a cylindrical silicon pillar structure arranged in a hexagonal lattice, and simulations indicate a uniform transmission amplitude across the phase spectrum. Mode decomposition analysis confirms that the generated vortex beam maintains a high purity of 98% for a topological charge of 2, demonstrating its potential to enhance terahertz communication and high-resolution imaging systems.