An optical millimeter-wave system based on optical heterodyne technology is proposed. The system realizes the parallel transmission of multi-frequency millimeter wave signal. In this scheme, CW Laser Array is used as the system light source. CW produces multiple emission laser frequencies and one local oscillator laser frequency (LO). Single-mode fiber (SMF) transmits multiple optical frequencies from a central station (CS) to a base station (BS). The photodetector (PD) beats to obtain millimeter-wave signals in multiple frequency bands. In this paper, simulation experiments are carried out based on four-frequency RoF channel. The minimum bit error rates of 39 GHz, 60 GHz and 80 GHz mmwave signals are 5.56×10^-157, 0 and 8.12×10^-28, respectively. The feasibility and good performance of the system are verified by the simulation results of spectral map, eye map and bit error rate. The influence of system phase noise and laser linewidth is discussed. The experimental results show that the system has a good effect of photogenerated millimeter wave and parallel transmission of multi-band signals. The results show that the desired baseband signal can be effectively restored under BS. This research provides support for the future development of fiber optic wireless communication.