To meet the requirements of demultiplexing in wavelength division multiplexing (WDM) systems for medium- and high-quality signal transmission, this study investigates two aspects: the elimination of crosstalk and the improvement in the wavelength drift of concave echelle grating (CEG) demultiplexing devices. The design used to eliminate crosstalk is summarized into three structures: Roland circle, non-Roland circle, and multiple grating cascade are presented and analyzed. To improve the wavelength shift, two methods—compensating polarization and flattening passband, are evaluated. Further, in introducing the demultiplexing principles, we review the research progress on crosstalk elimination and wavelength shift improvements and analyze the advantages for the proposed methods of eliminating crosstalk and improving wavelength shift. Additionally, the conditions for eliminating crosstalk and wavelength shift improvements are identified, and the potential future development directions of demultiplexers are discussed.