The　assembly　line　worker　assignment　and　balancing　problem　(ALWABP)　is　a　hot　and　interesting　topic.　In　an　assembly　line,　persons　with　disabilities　can　be　employed　and　work　better　due　to　the　specialized　work.　In　this　paper,　we　investigate　the　ALWABP　with　heterogeneous　workforce　considering　stochastic　worker　availability.　The　problem　has　been　addressed　in　the　previous　literature.　However,　the　workers　are　sometimes　insufficient　to　meet　all　stations　due　to　high　level　of　workforce　absenteeism　and　this　situation　has　not　been　fully　considered　in　the　literature.　Therefore,　we　propose　an　improved　two-stage　stochastic　programming　model　allowing　inadequate　workers　to　minimize　the　weighted　sum　of　cycle　time　and　penalty　cost　caused　by　insufficient　workers.　The　first　stage　is　to　assign　fixed　tasks　to　stations,　and　the　assignment　of　flexible　tasks　and　workers　is　regarded　as　the　second-stage　decision.　Sample　average　approximation　(SAA)　is　applied　to　solve　the　model　within　feasible　time.　Finally,　we　conduct　computational　experiments　to　test　the　model　compared　to　the　model　with　the　assumption　that　the　number　of　workers　is　adequate　to　meet　the　number　of　stations　(AS　model).　We　test　two　instances　including　8　and　10　tasks　respectively　and　different　numbers　of　scenarios　are　also　taken　into　account　to　demonstrate　the　improvement　of　our　model.　©　2019　IEEE.