A risperidone sustained release microsphere formulation is provided. The microsphere formulation comprise risperidone or 9-hydroxy risperidone or salts thereof, and a polymer blend having a first uncapped lactide-glycolide copolymer and a second uncapped lactide-glycolide copolymer, in which the first uncapped lactide-glycolide copolymer is a copolymer with a high intrinsic viscosity and the second uncapped lactide-glycolide copolymer is a copolymer with a low intrinsic viscosity. The sustained release microsphere formulation according to an embodiment of the present disclosure is suitable for large-scale industrialized production with improved stability, the in vivo release behavior of which will not change after long-term storage.