A　unit　cell　approach　is　employed　to　predict　the　effective　moisture　diffusion　property　in　fiber-reinforced　biopolymer.　The　permeable　fibers　distributed　in　the　matrix　are　taken　as　inclusion　phases　in　the　system.　Based　on　a　unit　cell　model,　the　calculation　method　for　moisture　diffusion　coefficients　is　developed　in　this　paper.　Moisture　diffusion　property　and　effective　diffusion　coefficients　are　numerically　investigated　under　different　temperature　and　volume　fractions　of　fibers.　The　calculated　results　agree　well　with　Gueribiz＇s　solutions.　Therefore,　it　is　reliable　in　predicting　moisture　diffusion　property　of　composite　using　the　unit　cell　model.　The　present　result　shows　that　the　effective　diffusion　coefficient　of　a　composite　depends　on　both　temperature　and　volume　fraction　of　fibers.　The　effective　diffusion　coefficient　of　regular　hexagon　pattern　composite　is　larger　than　that　of　square　pattern　at　the　same　temperature　and　volume　fraction.　©　2010　Higher　Education　Press　and　Springer-Verlag　Berlin　Heidelberg.