The invention discloses a method for deeply treating low-concentration printing and dyeing wastewater. The method has the advantages that quick adsorption treatment can be carried out on the low-concentration printing and dyeing wastewater by adsorbents, and accordingly water which is already subjected to adsorption treatment can reach standards and can be discharged or reused; adsorbed adsorbents can be treated by solvents to be desorbed and then can be regenerated and reused, desorption liquid becomes high-concentration wastewater, the water volume is 1/100-1/200 of the original treatment water volume, and accordingly the volume of wastewater required to be treated can be reduced to a great extent; oxidative degradation treatment is carried out on high-concentration desorption concentrated liquid by the aid of advanced oxidation technologies, the biochemical degradation performance of the high-concentration desorption concentrated liquid can be improved, B/C values of the high-concentration desorption concentrated liquid can be increased and are higher than 0.3, then the high-concentration desorption concentrated liquid is fed into a biochemical reaction system, low-cost biochemical degradation can be carried out, and the low-concentration printing and dyeing wastewater can be ultimately deeply comprehensively treated; the method includes simple processes and is low in investment cost, and influence on original processes can be prevented when existing processes are transformed and upgraded.