The up conversion method of radio-over-fiber (ROF) system is theoretically investigated and simulated,which is the key technique of ROF system. Based on optical carrier suppression,the 60 GHz optical-wireless signal is generated by the 30 GHz local oscillator in central station (CS). The up conversion procedure also take effect in CS,thus the local oscillator is not needed in the base station (BS). The cost is cut down by this method. Thus the growing need of the high frequency telecommunication can be met. Also,the simulation system is set up to testify the transmission performance of the ROF signal.