A new microwave photonic phase shifter based on polarization modulation with capability of frequency doubling is proposed and analyzed in this paper. A +1st order sideband signal with a carrier signal and a -1st order sideband signal with a carrier signal are producted by a dual-polarization Mach-Zehnder modulator (DPol-MZM) instead of the conventional polarization modulator, which are then sent to a fiber Bragg grating (FBG) used as an optical filter to filter out 1st orthogonal sidebands signals. By adjusting the polarization direction of the polarizer and beating 1st orthogonal sidebands signals at a photodetector, a frequency-doubled microwave signal is generated and its phase is continuously tunable by tuning the polarization controller (PC2). Taking advantages of the ability of frequency doubling and using PC tune, the frequency tuning range can be wider and fully tuned over 360°. By theoretical analyses and simulated verifications, a wideband frequency-doubling microwave signal with full range phase shift is achieved.