Refractory organic matter refers to the slow rate of decomposition by microorganisms, which decomposes incomplete organic matter (also includes metabolites of certain organic matter). The effective secondary treatment process mainly removes all biodegradable organic substances in sewage, and its removal rate is generally about 90%. Difficult-to-biodegrade organics generally cannot be removed during secondary treatment. These organic substances are easily enriched in organisms and become potential sources of water pollution. In the advanced sewage treatment process, it is necessary to effectively remove the refractory organic matter in the secondary treated water. The refractory organic substances in the secondary treated water are mostly lignin, humus, ethers, polycyclic aromatic hydrocarbons, benzidine, halomethane, methyl blue active substances (MBAS), herbicides and pesticides (such as DDT), etc. For the removal of these substances, it is suitable to use activated carbon adsorption and ozone oxidation from the perspective of economic rationality and technical feasibility.