The　zirconium　alloy　cladding　tube　and　end　plug　used　for　nuclear　fuel　rods　are　usually　joined　by　pressure　resistance　welding.　And　the　service　performance　of　the　fuel　rod　cladding　is　directly　influenced　by　the　welded　joint.　In　order　to　understand　the　forming　process　deeply,　an　axisymmetric　electro-thermal-mechanical　process　finite　element　model　was　established　in　this　paper.　The　current　density　distribution,　temperature　field　evolution,　and　joint　forming　process　during　pressure　resistance　welding　were　all　simulated　by　this　model.　It　was　shown　that　due　to　the　contact　resistance,　a　concentrated　heat　flow　was　rapidly　generated　on　the　tube-plug　contact　surface　caused　by　welding　current.　A　heat　conduction　was　established　on　both　sides　of　the　welding　surface.　The　high-temperature　region　on　the　side　of　the　cladding　tube　was　larger　than　the　end　plug.　The　metal　of　the　tube　extruded　to　both　inside　and　outside　of　the　joint　under　the　coupled　loading　of　heat　and　pressure.　The　location　of　the　highest　instant　temperature　on　the　welding　surface　moved　from　the　inside　to　the　outside　of　the　joint.　The　highest　temperature　was　1568　degrees　C,　not　reaching　the　melting　point　of　zirconium　alloy.　The　joining　area　and　the　highest　temperature　increased　with　welding　current　increasing,　the　welding　time　had　little　effect　on　them.　Based　on　the　numerical　model,　two　structural　design　schemes　to　improve　the　joint　forming　quality　were　proposed.　They　were　expected　to　provide　a　guide　line　for　the　joint　design.