We proposed and verified a simple precoding-less scheme to generate quadrature phase shift keying (QPSK) modulated vector millimeter-wave signal based on a dual parallel phase modulators (PM). The electrical vector data was first up-converted to achieve a 12 GHz radio frequency (RF) vector signal, then the RF vector signal was added with the other unmodulated RF source at 18 GHz, of which the generations were enabled by a digital signal processing (DSP). Next, the coupled RF source drove a PM to generate multi-frequency optical sidebands. A wavelength selective switch was adopted to pick out two optical sidebands at different frequencies which would beat frequency in the photodetector (PD). In this scheme, we set up a simulation platform to generate 48 GHz QPSK modulated vector millimeter-wave signals and analyzed the performance. The results showed when the input power for the generated 1-Gbaud/s vector millimeter-wave into PD is not less than −18 dBm, the bit-error ratio could be below 3.8×10−3, which demonstrated that the generated vector millimeter-wave signal enabled by our proposed scheme could work well.