Abstract In order to quantitatively analyze the clog problem of constructed wetland (CW), it is necessary to establish appropriate classification and extraction methods of clog components. This study was intended to use five kinds of substances, which were proteins, polysaccharides, humic acids, nucleic acids and inorganic substances, to describe CW clog quantitatively. These substances accounted for about 71% of the total mass of the clog. The method is proved to be feasible and could provide quantitative analysis for study on the mechanism of clog. In CW clog, the proportion of proteins, polysaccharides, humic acids, nucleic acids and inorganic substances was 9.86%, 1.90%, 5.68%, 3.95%, 49.87%, respectively. The best way to extract components from the CW clog is to use the method of “alkali wash+hot alkali+low-speed centrifugal” (AKAKL). Due to its simplicity and feasibility, the method could be performed in each common laboratory and more importantly, it is controllable with low cost and strong anti-interference.