A　new　mass　transfer　model　for　oil-containing　waste　water　treatment　by　low-pressure　hollow-fiber　ultrafiltration　(HFUF)　membrane　was　developed,　which　considered　the　axial　variation　of　pressure　and　local　permeation　rate　owing　to　the　variation　appeared　obviously　along　the　axial　distance　under　low-pressure　conditions　in　practical　HFUF　process.　The　numerical　simulation　was　performed　by　using　the　orthogonal　collocation　method　(OCM)　combined　with　MATLAB　software.　The　predicted　results　and　linear　relationship　of　total　permeation　rate　with　inlet　pressure,　simulated　by　this　model,　were　in　perfect　agreement　with　the　experimental　data,　which　verified　the　rationality　of　the　model　and　the　reliability　of　the　computing　method.　The　simulation　shows　that　radial　Peclet　number,　representing　the　influence　of　membrane　configuration,　solution　properties　and　fluid　movement　on　HFUF　process,　affected　distinctly　the　radial　and　axial　profile　of　local　or　mixing-up　concentration.　The　radial　velocity　inside　the　hollow-fiber　had　a　maximum　value　because　of　an　opposite　interaction　between　the　pressure　driving　force　from　hollow-fiber　center　to　membrane　wall　and　the　diffusion　behavior　due　to　the　reversed　concentration　gradient.　The　average　permeation　rate　decreased　in　pace　with　the　axial　distance　increasing,　therefore　the　final　hollow-fiber　length　would　depend　on　UF　efficiency　and　membrane　module　cost.　Also,　the　combination　algorithm　of　OCM　and　MATLAB　software　displayed　its　evident　advantages　of　less　computer　memory　space　and　CPU　time.　It　might　be　said　that　the　model　and　the　whole　simulation　software　could　be　employed　to　provide　a　suitable　selection　of　HFUF　membrane　type　and　technological　conditions　in　both　engineering　design　and　actual　operation.