This study was designed to systematically investigate the characteristics of bovine serum albumin (BSA) loaded poly(epsilon -caprolactine) (PCL) microparticles based on a 2(+) factorial experiment. The influences of polyvinyl pyrrolidone (PVP) concentration, BSA/PCL ratio, w/o/o/o ratio, and PEG/PCL ratio on the surface morphology, particle size, as well as the yield of microparticles, encapsulation efficiency of BSA, and in vitro release properties were evaluated. The microparticles were prepared by the w/o/o/o solvent evaporation method. The structure of BSA retained its integrity using this technique. The mean particle sizes of BSA-loded microparticles were in the range of 20-50 mum, and a highly porous morphology existed in these microparticles, irrespective of the formulations. The production yields of microparticles were in the range of 52.1-89.0%, and the encapsulation efficiencies were in the range of 13.8-68.3%. The burst release of BSA was in the range of 6.9-69.0%. The volume ration of the multi-phases significantly affected the encapsulation efficiency of BSA in PCL microparticles, and the initial amount of BSA encapsulated by PCL in terms of BSA/PCL ratio significantly affected the amount of BSA released at the end of 14 days (p < 0.05).