Here, we begin with analyzing the principle of phase modulation mechanism of metasurface, and then discuss how to utilize multiple degrees of freedom to achieve multifunctional optical response. For a proof of concept, we design several metasurfaces composed of amorphous silicon (a-Si) nanorods to demonstrate the multichannel control of light with different phase mechanisms. This study provides theoretical support for flexible design of metasurfaces, and introduces and gives a summary of the research progress of multifunctional meta-devices.