As the potential of the OAM beam on wireless communication area was discovered by engineers, more and more attentions have been drawn into the OAM beam generating area. Metasurface as a two-dimensional resonant structure has become a popular method to generate the OAM beam efficiently. However, when the topologic number of the OAM beam comes to 4, the OAM beam generated by the metasurface has a high sidelobe level (SLL) appeared at the direction of propagation which will affect the distribution of the near-field and purity. In this paper, the reason why there is a large sidelobe at the propagation direction is analyzed through analysis method of array antenna. And then, based on the analysis, a hexagonal reflective meta-atom is designed and simulated. The designed meta-atom works at 10GHz and has a 2GHz bandwidth. And simulation results show that the phase range of the meta-atom manipulation can cover 0 to $2\pi$. Finally, a reflective metasurface combined by the hexagonal meta-atom is designed and simulated. And the simulation results show that the sidelobe level along the propagation direction of a 4-order OAM beam generated by a hexagonal metasurface is 20dB lower than that of a quadrilateral metasurface.