OBJECTIVE The influence of the theoretical drug loading on the physicochemical properties of the polyethylene glycol-poly lactic acid-co-glycolic acid( PEG-PLGA) microspheres loaded bovine serum albumin( BSA) fabricated by SPG membrane emulsification was investigated. METHODS Encapsulation efficiency,drug loading and particle size were used to evaluate the physicochemical properties of the microspheres. The surface and internal morphology of the microspheres were investigated by scanning electron microscopy...