A water quality detection system includes a conveying module, multiple detection test papers, a supply module, a detection module, and a processing unit. The detection test papers are disposed on the conveying module in a continuous arrangement. The conveying module conveys the detection test papers along a conveying path to sequentially pass through a first position and a second position. The supply module supplies liquid to be tested to the detection test papers passing through the first position. The detection module captures a color signal of the detection test papers passing through the second position. The processing unit generates a water quality signal according to the color signal.