Abstract: The spectral analysis method can be used to qualitatively and quantitatively research water quality parameters using the characteristics that the molecules or ions of substances in the solution can absorb the full spectrum of ultraviolet-visible light. It enjoys the advantages such as high detection speed, low cost, in-situ measurement, no secondary pollution, and the simultaneous online monitoring of multiple water quality parameters. Based on the statement of the theoretical basis of water quality spectrum analysis, this paper systematically analyzes the principles and characteristics of various measurement methods. By comparing domestic and foreign full-spectrum water quality online monitoring devices, this paper points out the key technological difficulties in the establishment of high-precision online inversion models of water quality parameters and further proposes the development trends of multi-parameter online monitoring systems of water quality using the spectral analysis method. Therefore, this paper will provide a reference for the research on water environment monitoring technologies and the development of instruments for water quality parameter detection based on the theories of spectral analysis.