The principle of silicon dioxide online monitoring instruments is mainly based on the photometric method. By using light of a specific wavelength passing through a solution containing silica, the amount of light absorbed is proportional to the concentration of silica in the solution. By measuring the absorption of light, the concentration of silica is quantitatively analyzed. It features high precision and high sensitivity, capable of accurately and real-time reflecting the silica content in water quality, providing reliable data support for water quality monitoring.