The invention relates to a reducing and recycling treatment method for biological activated sludge, belonging to the sludge treatment field. The method comprises the following steps: biological activated sludge is transported to a sludge storage tank, is stirred and concentrated, and then is oxidized and disinfected by adding an oxidizing agent so as to destroy cell walls of microbes in sludge and reinforce deprivation of bound water in sludge so that the moisture content of sludge is reduced to below 95%; a dehydrating agent is added so as to increase solid compositions and improving the effect of breaking away from water; then the uniformly-mixed sludge is pumped to a diaphragm type plate-and-frame filter press to maintain pressure for strong force pressing; the pressed blocky sludge is piled up at a ventilating place for week so as to be dried naturally till the moisture content is reduced to below 35%; and finally, the sludge is composted or mixed into coal so as to be burned in a boiler, and adsorbed water, bound water and residual void water and cellular moisture in sludge are removed during burning. The method causes the sludge to be completely reduced in weight, stabilized and harmless and simultaneously realizes the recycling utilization of self-heating or external heating.