In radio-over-fiber(ROF) systems,in order to up-convert the optical baseband signals containing information to the microwave/millimeter wave band,this paper proposes a kind of photonic up-conversion,which is based on the cross gain modulation(XGM) and the cross phase modulation(XPM) effects in semiconductor optical amplifier(SOA).The 1.25 Gb/s signal is up-converted to 30 GHz milli-meter wave.The performance of up-conversion in XGM effect is analyzed by varying SOA current(50-200 mA) and signal wavelength.Under-2 dBm optical power for optical-electrical conversion,the power of 30 GHz millimeter wave in XPM blue chirp up-conversion,red chirp up-conversion and XGM up-conversion is-16.6 dBm,-16.7 dBm and-32 dBm,respectively.