In this study, polyethersulfone (PES)-alginate microcapsules were prepared for drug-controlled release, and vitamin B-12 (VB12), rifampicin (RFP), and bovine serum albumin (BSA) were used as model drugs. Different micro-capsules were prepared by the variation of the crosslinking degree of alginate and the variation of the chemical components of the microcapsule membrane, including the PES and polyethylene glycol (PEG) contents. Systematic experiments were carried out to study their influences on the release profile of the model drugs. The results showed that with the increase of the crosslinking degree of the alginate, the drug release rate increased; whereas with the increase of the PES concentration used to prepare the microcapsule membrane, the drug release rate decreased. The contents of the PEG in the microcapsule membrane also affected the drug release. This study enriched the methodology of the fabrication of the microcapsules, and the microcapsules may have a potential use for controlled release. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 111: 651-657, 2009