The invention relates to the field of environmental protection, and discloses a method for treating low-temperature flue gas. The method comprises the following steps: (1) carrying out gas-liquid contact reaction on the low-temperature flue gas and a liquid complexing agent to obtain a failed liquid complexing agent and flue gas from which nitrogen oxides and hydrogen sulfide are removed; (2) quenching and tempering the failed liquid complexing agent obtained in the step (1) to obtain a quenched and tempered liquid complexing agent; and (3) regenerating the quenched and tempered liquid complexing agent obtained in the step (2) to obtain a regenerated liquid complexing agent. The method can simultaneously remove nitrogen oxides and hydrogen sulfide in the low-temperature flue gas, and overcomes a problem that the low-temperature flue gas needs to be heated and then treated in a traditional method, and can directly perform gas-liquid contact reaction with the low-temperature flue gas. According to the method, the liquid complexing agent can be regenerated, so that recycling of the liquid complexing agent is realized. The method has characteristics of environmental protection, resource saving and good recyclability.