Aim at the transmission capacity and the mode crosstalk of mode divi sion multiplexing (MDM) system,we design and set up a new-type 6×6multiple input multiple outp ut (MIMO) MDM system with the VPItransmissionMaker simulation platform.This system uses a phot onic crystal few-mode fiber (FMF) which has high mode differential group delay (MDGD),and the transmissions of all modes including LP₀₁,LP_11a,LP_11b,LP_21a,LP_21b,LP₀₂ ar e relatively independent,combined with constant modulus algorithm (CMA) to achieve the output signal for de-multiplexing.The s imulation results show that when the signal to noise ratio (SNR) of this system is 22dB,each mode carries a transfer rate of 40Gbit/s signal by 4QAM modulation,transmit 34km in the photonic crystal FMF,and it ensures the bit error rate (BER) of each mode is under 10－5 orders of magnitude,which meets the minimum requirement of communication system transmission.Compared with MDM systems using traditional FMF,this system can effectively eliminate crosstalk between all modes,and it can significantly impr ove the capacity of MDM system,so it will have significant applications in the high-speed and large-ca pacity optical transmission system.