Polarization manipulation of electromagnetic wave or polarization multiplexed beam shaping based on metasurfaces has been reported in various frequency bands. However, it is difficult to shape the beam with multi-channel polarization conversion in a single metasurface. Here, we propose a new method for terahertz wavefront shaping with multi-channel polarization conversion via all-silicon metasurface, which is based on the linear shape birefringence effect in spatially interleaved anisotropic meta-atoms. By superimposing the eigen- and non-eigen-polarization responses of the two kinds of meta-atoms, we demonstrate the possibility for high-efficiency evolution of several typical polarization states with two independent channels for linearly polarized waves. The measured polarization conversion efficiency is higher than 70% in the range of 0.9–1.3 THz, with a peak value of 89.2% at 1.1 THz. In addition, when more other polarization states are incident, combined with the integration of sub-arrays, we can get more channels for both polarization conversion and beam shaping. Simulated and experimental results verify the feasibility of this method. The proposed method provides a new idea for the design of terahertz multi-functional metadevices.