A switchable metasurface with dual functions of polarization conversion and filtering is proposed in this paper. The designed structure is composed of a medium-metal-medium-metal-medium structure, and VO2 is embedded in the metal metasurface. When VO2 is an insulated state, this structure can perform linear polarization conversion under terahertz wave normal incidence, and it has good asymmetric transmission capabilities. At the range from 2.01 to 2.86 THz, the polarization conversion rate is higher than 93%. When VO2 is in the metallic state, the structure becomes a broadband band-stop filter with a 3 dB bandwidth of 1.73 THz. The polarization conversion and filtering functions of the proposed structure can be converted to each other by changing the external temperature. This switchable multifunction structure provides a new way for the design of terahertz devices.