For　the　streamline　curvature　inverse　proposition　design　of　a　full　three-dimensional　centrifugal　impeller,　a　new　finite　difference　method　is　put　forward　to　solve　the　S2m　stream　surface　velocity　gradient　equation.　In　the　difference　scheme,　forward　difference　is　chosen　for　the　relative　velocity　derivative　along　the　quasi　orthogonal　curve;　that　along　the　streamline　direction　is　decomposed　into　two　items,　forward　difference　is　used　for　first　item,　backward　difference　for　another,　and　forward　difference　for　all　other　parameter　derivatives.　The　scheme　solves　the　difficulty　to　guarantee　the　matrix　main　diagonal　elements　being　dominant　in　solving　velocity　field　with　simple　forward　difference　or　backward　difference　scheme,　and　has　higher　stability　and　convergence.　The　new　finite　difference　scheme　is　taken　to　redesign　Krain　impeller.　The　CFD　analysis　shows　that　modified　impeller　efficiency　is　increased　by　0.3%,　and　compression　ratio　is　heightened　0.2.　©,　2015,　Xi＇an　Jiaotong　University.　All　right　reserved.