Aiming at the poor quantization performance of low bit digital analog converter(DAC) in intensity modulation direct detection-filter bank multi-carrier(IMDD-FBMC) system, a non-uniform quantization scheme based on signal distribution estimation is proposed. The scheme uses the non-linear programming method based on FBMC signal distribution to obtain the quantitative step when the quantization error is minimum, and then improves the performance of IMDD-FBMC system based on low bit DAC. The simulation results show that the proposed scheme can improve the BER performance of the IMDD-FBMC system by 15.9~60.7 times under the condition of 3~5 bit quantization number compared with the uniform quantization scheme, and the quantization scheme based on signal distribution can reduce 1~2 bit quantization number and reduce the system cost under the condition of ensuring the system performance.