This paper focuses on the standard chemical oxygen demand (COD) liquid and studies the impact of pH, nitrite nitro-gen, nitrate nitrogen, heavy metals, salinity, and other factors on fluorescence intensity and fluorescence peak posi-tions during the detection of COD in water using fluorescence spectrometry. The influence mechanisms of different environmental factors on fluorescence spectra are also analyzed. Results indicate that pH value affects the fluorescence emission wavelength (Em), resulting in a red shift from 1.5 to 7.2, and a blue shift from 7.2 to 12.3. Nitrate nitrogen can react with organic matter in water to form nitro compounds, leading to a decrease in fluorescence intensity. Salin-ity has a negligible effect on T1 peak but a relatively large effect on T2 peak. Heavy metal ion concentration has a sig-nificant impact on T2 peak, while T1 peak position shifts with an increase in heavy metal ions. This study aims to ex-plore the factors that can impact the detection of COD in water using three-dimensional fluorescence spectrometry, providing references to improve accuracy and practicability for COD detection based on three-dimensional fluores-cence spectrometry.