A novel scheme is proposed for generating high quality frequency octupling signal, which can be used in millimeter-wave radio-over-fiber (RoF) system. It′s based on an integrated structure of triple-parallel Mach-Zehnder modulator (MZM) by using two adding one structure. Two kinds of redundant sidebands are well eliminated by adopting 90\O of the electric phase-difference between two sub Mach-Zehnder modulators (sub-MZMs), driven by radio frequency (RF) signal. Moreover, bias of the third sub Mach-Zehnder modulator (sub-MZM) is tailored to get the best signal. The simulation results show that the radio frequency spurious suppression ratio (RFSSR) is as high as 38.3315 dB under the condition of conventional extinction ratio (30 dB) without any optical or electrical filter. Furthermore, optical sideband suppression ratio (OSSR) can reach as high as 61.22878 dB at ideal extinction ratio (100 dB). For not only conventional condition but also the ideal case, the scheme can get high quality millimeter-wave signal.