Using Y-G algorism, substituting the descrete components such as gratings, and lenses by two binary phase-only elements H1 and H2, the new type phase-only wavelength division multiplexer (WDM) is designed. The phase modulation of H1 makes the intensity distribution on the output plane H2 satisfied to the design such that eight Gaussian beams are arrayed according to their wavelengths and their crosstalk is little. H2 transforms the wavefront of the output laser beam to couple well to each receiving channel. By only phase modulation, the demultiplexer, focusing etc. of the WDM are realized.