Water quality monitoring technology based on optical method is the trend for modern water environmental monitoring. Compared with the traditional monitoring methods, Spectroscopy is a more simple, a small amount of reagent consumption, good repeatability, high accuracy and rapid detection of significant advantages, which is very suitable for rapid and on-line monitoring determination of environment water samples COD. This paper summarized the status and research progress of optical methods for monitoring of COD in water. The basic principle of traditional analysis methods and optical methods for measuring COD in water were brief described, and compared to the characteristic of different waveband of the detection of COD. The principles and applications of spectroscopic methods commonly used spectral preprocessing methods and calibration methods were listed, and also introduced the progress of optical sensors. Finally, the future research focus and direction of spectroscopic methods were prospected.