Chemical oxygen demand (COD) is a synthetic indicator that represents the degree of organic pollution in water. Compared with the conventional wet chemical method, near-infrared (NIR) transmission and ultraviolet (UV) absorbance method based on photoelectric detection technology and spectroscopy analysis offer advantages such as high precision, speed, non-contact, and absence of secondary pollution, to name a few. NIR transmission spectra and UV absorbance spectra of standard solution configured with phthalate hydrogen potassium were collected using multi purpose analyzer (MPA) Fourier transform infrared (FT-IR) spectrometer and AvaSpec-2048-2 UV spectrometer, respectively. After different pretreatment of the spectra, COD quantitative analysis model was established using partial least squares (PLS) regression and linear regression. The statistical analysis of COD quantitative model was implemented, and the result revealed that UV absorbance method had higher relevance but lower forecast accuracy and precision than the NIR transmission method.