Based on the concepts of the 2-dimension diffraction grating and the planar waveguide array,a novel optical multiplexer/demultiplexer (Mux/Demux) employing the 2-dimension arrayed-waveguide grating is proposed.Since the direction of the diffraction route is determined by the vectorial combination of the dispersion values in two directions,the 2-dimension wavelength demultiplexing can be realized by properly controlling the values of the free spectral ranges.Then the input and output accessing ports of the Mux/Demux can be set in 2 diemnsions,with which the capability to design high-channel-count optical Muxs/Demuxs is improved.The properties and the possible applications of this Mux/Demux are discussed in this paper.