Photonic generation of frequency octupling microwave signal is proposed and demonstrated, which is based on a cascading polarization modulator and a dual-parallel Mach–Zehnder modulator. The method avoids using phase shifter and optical filter, which is suitable for generating a frequency octupling microwave signal with a wideband tuning range and fast tuning speed. In the experiment, a photonic generation frequency octupling microwave signal with 20 GHz is generated. The optical sideband suppression ratio, electrical sideband suppression ratio (ESSR), and phase noise of the photonic generation octupling microwave signal are measured. In addition, the tunability of the proposed scheme is investigated.