The asymmetric transmission (AT) and polarization conversion of terahertz (THz) wave play a vital role in future THz communication, spectrum, and information processing. Generally, it is very difficult and complicated to actively control the AT of electromagnetic (EM) wave by using traditional devices. Here, we theoretically demonstrate a stereo-metamaterial (stereo-MM) consisting of a layer of metal structure and a layer of phase transition structure with a polyimide spacer in between. The performance of the device is simulated by using the finite-integration-technology (FIT). The results show that the AT and polarization conversion of linearly polarized wave can be dynamically controlled in a range of 1.0 THz–1.6 THz when the conductivityσof vanadium dioxide (VO2) is changed under the exteal stimulation. This study provides an example of actively controlling of the AT and polarization conversion of the EM wave.