This paper proposes a switchable multifunctional metamaterial device operating in the terahertz (THz) band. The device is loaded with an equivalent diode and utilizes vanadium dioxide (V O 2). The middle layer of the whole device, a metal layer, divides the device into the I side and the II side. When the diode is ON, the I side can achieve dual-band absorption at 1.975 and 4.345 THz. When the diode is OFF, the I side can achieve single-band absorption at 4.28 THz. In the case of V O 2 being insulating, the II side can achieve linear-to-linear (LTL) polarization conversion at 2.342-4.18 THz. In the case of V O 2 being conductive, the II side can realize linear-to-circular (LTC) polarization conversion at 2.105-3.283 THz. The device provides a new strategy for the subsequent combination of multiple functions. The device can be used in electromagnetic stealth, intelligent applications, radiometers, and sensors and has relatively large application potential in miniaturized multifunctional metamaterials and THz band research.