Composite microparticle drug delivery systems based on chitosan, alginate and pectin with improved pH sensitivity were developed for oral delivery of protein drugs, using bovine serum albumin (BSA) as a model drug. The composite drug-loaded microparticles with a mean particle size less than 200 μm were prepared by a convenient shredding method. Since the microparticles were formed by tripolyphosphate cross-linking, electrostatic complexation by alginate and/or pectin, as well as ionotropic gelation with calcium ions, the microparticles exhibited an improved pH-sensitive drug release property. The in vitro drug release behaviors of the microparticles were studied in simulated gastric (pH 1.2 and pH 5.0), intestinal (pH 7.4) and colonic (pH 6.0 and pH 6.8 with enzyme) media. For the composite microparticles with suitable compositions, the releases of BSA at pH 1.2 and pH 5.0 could be effectively sustained, while the releases at pH 7.4, pH 6.8 and pH 6.0 increased significantly, especially in the presence of pectinase. These results clearly suggested that the microparticles had potential for site-specific protein drug delivery through oral administration. ©2008 Elsevier B.V. All rights reserved.