The invention relates to a method for desulfurizing and denitrating boiler gas simultaneously by using active carbon under microwave radiation, which is used for solving the problem of removing sulfur dioxide and nitrogen oxide. The technical scheme is achieved as follows: dedusted gas is introduced into an active carbon bed, is desulfurized and denitrated under the condition that active carbon is heated 400-600 DEG C by microwave, and 10-30kg of CuCl is added into per cubic meter of active carbon to be used as a catalyst. The invention greatly improves the desulfurizing rate and the denitrating rate by using the selective heating property of the microwave and combining the reducing capacity of the carbon to SO2 and NOx, and can achieve desulfurizing rate above 95 percent and denitrating rate above 90 percent. The CuCl catalyst is coated on the surface of the active carbon, therefore, the invention can obviously reduce the denitrating reaction temperature, not only reduces the loss of the active carbon, but also improves the reaction condition, and is beneficial to the recovery of elemental sulfur.