A new approach is proposed to enable a beam to carry orbital angular momentum (OAM) and manipulate the OAM of vortex beams by using metasurface. In the evolution of the polarization state, the light field can acquire a Pancharatnam-Berry(PB) geometric phase. Then it is possible to obtatin a desired phase by manipulating the polarization of light. The metasurface constructed in this paper has a distribution of spatially varying optical axes, and can manipulate the polarization of light accurately. Particularly, if the optical axis orientation of metasurface changes continuously along the azimuth direction, an azimuth-dependent PB phase, i.e. a vortex phase, will be imparted to the beam. Such a phase can be used to enable a beam to carry OAM and tune the OAM of a vortex beam. Further experiments verify the theoretical results. The results provide a new way to generate OAM beams and modulate their OAM, which is expected to have potential applications in quantum communication and optical micromanipulation.