Water quality on-line monitoring method and device

The invention discloses a water quality on-line monitoring method and a water quality on-line monitoring device. The water quality on-line monitoring method comprises the following steps of: S1, in a detection model construction stage, obtaining a relation between the test paper color change and the detection index concentrations, and constructing a detection model; S2, in an information acquisition stage, dropping a sample onto a test paper layer, wherein the test paper layer displays different colors because of different detection index concentrations, and acquiring color change image information on line; S3, in a characteristic quantity stage, preprocessing acquired original data, then extracting characteristic quantities, and extracting image information of the test paper layer; and S4, in a detection and judgment stage, performing characteristic layer fusion processing on the extracted image information characteristic quantities, and performing on-line detection through the constructed on-line monitoring model. The water quality on-line monitoring method can measure the pollutant content of water quickly and accurately in real time and evaluate the quality of a water body; and furthermore, the detection device is light in structure, simple in operation and low in cost and has a direct practical significance for monitoring of the quality of the water body and guaranteeing of the sustainable development of agriculture.