An approach to achieving continuously tunable microwave/millimeter-wave frequency multiplication signal based on injection locked dual-wavelength difference-frequency distributed feedback (DFB) laser is proposed. Wave optical signals are nonlinearly broaden by semiconductor optical amplifier (SOA), and high-order components are generated. The sine wave optical signal is injected into two DFB laser and locked enlarge, then the continuously tunable frequency multiplication is generated. In the experiment, the injected sine wave optical signal frequency is 1.25 GHz, the continuously tunable microwave signal with any natural multiples of 1.25 GHz in the 20~40 GHz frequency range is achieved, and the highest multiplier of 32.