The　secondary　flows　generated　by　the　rib　and　the　U-shaped　bend　play　a　vital　role　in　heat　transfer　enhancement　in　two-pass　ribbed　channels.　This　paper　focuses　on　the　combined　effects　of　rib　orientations　(N-type　and　P-type)　and　rib　angles　(from　30A　to　75A)　on　flow　and　heat　transfer　in　two-pass　ribbed　channels.　The　3D　steady　Reynolds-averaged　Navier-Stokes　equations　coupled　with　SST　k-omega　model　are　solved　by　using　commercial　software　ANSYS　CFX.　The　CFD　model　has　been　validated　by　experimental　data　with　a　good　agreement.　In　addition,　the　comprehensive　evolution　of　secondary　flows　and　its　effect　on　heat　transfer　are　analyzed　in　detail　by　using　vortex　core　technology.　The　results　indicate　that　the　key　factor　for　local　heat　transfer　enhancement　is　to　transport　more　secondary　flows　into　downstream　passage　without　weakening　local　secondary　flow　and　energy　dissipation　of　upstream　secondary　flow.　Furthermore,　the　rib　orientation　in　passage　2　should　consider　the　influence　of　rib　angle　so　that　the　local　main　flow　secondary　flow　has　the　same　rotational　direction　with　the　most　powerful　upstream　secondary　flow　to　reduce　the　energy　loss　and　speed　up　the　growth　of　local　main　flow　secondary　flow　as　much　as　possible.