A　simple　semi-theoretical　steady-state　model　for　the　convective　flux　in　cross-flow　microfiltration　has　been　developed　based　on　the　mass　balance.　The　model,　which　has　two　coefficients,　A　and　K,　can　describes　the　cake　increase　on　membrane　surfaces　in　a　hollow-fiber　membrane　module　and　predicts　its　membrane　flux　decline.　Then　this　model　was　validated　by　using　yeast　suspensions　in　a　0.1　mu　m　hydrophilic　polyvinylidene　fluoride　(PVDF)　hollow-fiber　membrane　module　with　a　0.3　m(2)　filtration　area.　The　experimental　and　analysis　results　showed　that　the　two　coefficients,　A　and　K,　actually　varied　in　a　small　range,　but　when　the　overall　average　values　of　A　and　K　were　taken　into　the　model　as　two　constants　under　the　different　operating　conditions,　the　experimental　observation　is　in　good　accordance　with　the　model　prediction　and　the　absolute　value　of　relative　error　is　less　than　7%.　So　it　was　advisable　to　consider　the　model　coefficients,　A　and　K,　as　two　constants　in　the　model　to　predict　the　steady-state　flux　decline　in　industrial　applications.