A novel photonic technique of millimeter-wave (mm-wave) sub-carrier generation using optical parametric loop mirror (OPLM) and fiber Bragg grating (FBG) is proposed. Due to the four-wave mixing (FWM) effect and loop reflection characteristic in an OPLM, a carrier-suppressed modulation signal is able to generate two new harmonic components with six times frequency spacing of the modulation frequency and the initial two optical tones can be reflected back to the input port by the OPLM itself, which servers as the first order filtering. At the transmission port of the OPLM, a matching FBG will give further suppressing on the pump light. Finally, a millimeter-wave sub-carrier will be obtained after the FBG.