Total phosphorus water quality on-line detection method

The invention discloses a total phosphorus water quality on-line detection method which comprises the following steps: sucking and storing a water sample of a river channel in a storage cabin by using a sampling device; discharging the water sample from the storage cabin by using a water outlet valve, mixing with a reagent, and feeding into a digestion device; performing digestion in different procedures inside the digestion device, and cooling the water sample after digestion; positioning the digestion device and a detector on a same straight line, powering on a detection light source, enabling the detection light source to penetrate through the digestion device, reading a light signal by using the detector, and calculating the total phosphorus content; transmitting data to a computer from the detector through wireless signals, preserving the data, and performing real-time on-line control; after the total phosphorus content is measured, conveying a waste liquid to a waste liquid treatment device for sterile