The invention discloses a printing and dyeing sewage classification treatment process. Printing and dyeing sewage is divided into two broad categories of chemical fiber sewage and cotton comprehensivesewage, the chemical fiber sewage is divided into two sub-categories of alkali-reduced sewage and chemical fiber general sewage, and then treatment is carried out; an alkali-reduced filtrate is incorporated into a chemical fiber general filtrate, subsequent physicochemical process is carried out after adjustment, a medicament can be effectively saved, and thus the operation cost is reduced; the cotton comprehensive sewage is subjected to alkaline process treatment, and is use as an alkali source for reversed adjustment of a mixed sewage III, and thus an alkali use amount of chemical fiber sewage can be saved; cotton desizing sewage, cotton printing sewage and cotton dyeing sewage are combined into one category of sewage, namely the cotton comprehensive sewage, the concentration of pollutants can be averaged each other through mixing of three kinds of sewage, and treatment difficulty is reduced; at the same time, a construction area is reduced; and a pH value of the cotton comprehensive sewage can be controlled centrally to create prerequisites for the next step of mixing with the mixed sewage III.