Abstract: A high speed long distance radio over fiber system based on double photoelectric arms coherent modulation and optical duobinary coding technology is proposed and demonstrated. Optical duobinary signal is built by the first photoelectric arms coherent modulation, in which occupancy bandwidth frequency spectrum is reduced by half than NRZ code. 40 GHz ultra high frequency microwave signal is loaded through second levels of photoelectric arms coherent modulation. The simulation results show that the 40 Gb/s data and UHF microwave with 40 GHz are successfully transmitted over 1 500 km distance of a singlemode fiber with a dispersion of 17 ps/(nm·km), attenuation of 02 dB/km, a light source power of 0 dBm, EDFA and dispersion compensation optical fiber.