A filter-less frequency doubling generator with tunable phase shift based on dual-polarization modulation is proposed and analyzed. The setup is composed with a continuous-wave laser, a dual-polarization Mach-Zehnder modulator and a linear polarizer followed by a photodetector. The modulator is used to generate frequency doubling modulation signals on orthogonal polarization axis. By tuning the polarization state before the polarizer, the initial phase of the generated microwave signal can be tuned manually. At the meantime, the signal amplitude will remain constant. It is found the generated signal's frequency is twice of the driven frequency. The electrical phase shift can be tuned within full range ((0°—360°). Without using any optical filter or wavelength-dependent component, this scheme is featured with good frequency tunability and multi-wavelength operation.