In this paper, we propose a novel microwave photonic phase shifter based on a polarization division multiplexing dual-parallel Mach-Zehnder modulator (PDM-DPMZM). In this scheme, by adjusting the direct current (DC) bias voltages, the PDM-DPMZM is employed to generate a frequency-doubled or frequency up-converted and down-converted signals with their phases tuned across a full range. The phase shift is changed just by tuning the angle α between the polarizer’s polarization direction and one of the principal axes of the modulator. Supported by the optical frequency comb, the system is easy to be extended to multichannel system with independent phase tuning capability. The simulation results show that a radio frequency (RF) signal with a frequency of 5 GHz can be converted into a 10-GHz frequency-doubled signal, a 1-GHz frequency up-converted signal, and a 13-GHz frequency down-converted signal. Their phases can obtain a full-range phase shift from -180°to 180°, and the power response of the generated signal with different phase changes is relatively flat.