The invention discloses a detection system and a detection method for organic matter components of sewage. The detection system for organic matter components of sewage comprises a closed vessel, a sealing plug, a splash-proof return hole ball, an electric mixer, an aerator, a dissolved oxygen probe, a temperature sensor, an electric heating rod, a temperature and dissolved oxygen determination instrument, a data signal input end, a computer, a data output end, a controller, a gas outlet valve relay, an electric heating rod relay, an electric mixer relay, an aeration relay, an air pump, and a gas outlet valve. The invention further discloses a method for detecting organic matter components of sewage by using the detection system. Based on an activated sludge model, the detection method disclosed by the invention divides the composition of sewage according to the biodegradation process of organic matters from the angle of biochemical reaction and according to the representation of existing forms from the angle of physical properties, and puts forward a determination scheme according to different mechanisms, improving the efficiency and accuracy of detecting organic matter components.