The invention relates to a biomass high solid anaerobic digestion process for the separation and backflow of active sludge, which comprises the following steps of: 1, adding biomass into a high solid anaerobic reactor, and discharging after a reaction; 2, centrifuging the discharged materials by using centrifugal equipment, wherein after centrifugation is performed, an upper layer is a supernatant liquid layer, an intermediate layer is a sludge layer, and a bottom layer is a residual residue layer; 3, allowing the intermediate sludge layer to flow back to the high solid anaerobic reactor, andadding the biomass into the high solid anaerobic reactor; and 4, discharging after the reaction, and circularly performing the steps 2, 3 and 4. By the process, the problems of low loads, long retention period of hydraulic power, incapability of separating the retention period of the sludge from the retention period of microbes and the like in the anaerobic digestion process are solved, the high-load, high-stability and high-efficiency running of the biomass high solid anaerobic digestion process can be ensured, and the high-efficiency energy utilization of the biomass is realized.