For the case that the minimum mean square error (MMSE) algorithm can not be used to realize the demultiplexing of mode-division multiplexing (MDM) when the mode dependent loss (MDL) is large, a demultiplexing method based on the successive interference cancellation (SIC) is proposed in order to nearly reach the performance of the maximum likelihood (ML) detection method. This method reduces the interference of the maximum power signal to the other signals and the aim for the compensation of MDL is obtained. Then the MMSE method is adopted to demultiplex the original signals. For the demultiplexing of a 6×6 MDM system under different coupling strengths as well as with and without MDL, the simulation results show that, the SIC-MMSE method always achieves good performance compared with the MMSE algorithm. The computational complexity is similar with that of the MMSE algorithm. With the differential mode group delay (DMGD) at 9 ps/km and coupling strength at -5 dB, the optical signal to noise ratio (OSNR) by the SIC-MMSE algorithm improves by 3 dB at a transmission distance of 1200 km compared with that of the MMSE algorithm.