In order to further improve the transmission capacity of the optical communication system, this paper proposes a two-wavelength ×three－mode hybrid multiplexer/demultiplexer based on photonic crystals. The device consists of three combined resonators, three wavelength selective reflection microcavities, single mode waveguides, multimode waveguides and tapered coupled waveguides. The filtering is realized by the structure of combined resonator and wavelength selective reflection microcavity, and the mode conversion is realized by the structure of the asymmetric parallel waveguide. The simulation analysis by time-domain finite difference method shows that the device can realize the multiplexing/demultiplexing of six channels, such as the 1530 nm TE 0 mode, 1530 nm TE 1 mode, 1530 nm TE 2 mode, 1550 nm TE 0 mode, 1550 nm TE 1 mode and 1550 nm TE 2 mode. Its insertion loss is <0.127 dB and the channel crosstalk is <-15.19 dB.