An improved method to generate optical single sideband with carrier (OSSB+C) signals is proposed based on the integrated Mach-Zehnder modulator(MZM) in the radio over fiber (RoF) system, avoiding the great difference of the power of optical carrier and that of optical sideband using the conventional OSSB+C modulation. By adjusting the direct current voltage applied in the direct current arm of the integrated MZM, the balanced power of the optical carrier and optical sideband is obtained for any modulation index, i.e. the optimum carrier-to-sideband ratio (CSR) value of 0 dB is achieved. The variation of CSR is then analyzed theoretically under different loss states of the integrated MZM. It is verified by the simulation results that adjusting the direct current voltage can make the power of optical carrier and that of optical sideband balanced. The simulation results also show that when the direct voltage deviates from the optimum value in the integrated MZM, the RoF system based on the proposed technique has better robustness if the bias drift is controlled within the range of 5%.