The invention discloses a method for improving the anaerobic digestion performance of biomass wastes by a biological phase separation and optimization technology and belongs to the technical field of treatment and recycling of the solid wastes. The technology is characterized in that: solid residue and liquid of materials are subjected to anaerobic digestion under different conditions, a liquid phase enters a methane production reactor directly, solid matter enters an acidification reactor, acidification phase starting optimization of two-phase anaerobic digestion is performed, and then a product enters the methane production reactor, and mass distribution of acidification and methanation phases is optimized, so the coupled linkage of the acidification phase and the methanation production phase is realized, different material components can be fully degraded, and the pH buffering capacity of a microorganism system can be improved; and therefore, the material inlet load of the whole system can improved, the volume of the reactor is reduced, treatment cost is reduced, and the conversion rate of the system is improved.