A　model　for　three-dimensional　transient　temperature　field　of　induction　motor　was　set　up　and　the　heat　exchange　between　stator　and　rotor　was　simulated　by　using　the　concept　of　＇equivalent　coefficient　of　heat　conductivity＇.　The　influence　of　temperature　rise　on　the　stator　and　rotor　resistance　was　considered　for　thermal　loss　calculation.　The　influence　of　the　end　of　stator　and　rotor　on　axial　temperature　distribution　was　also　taken　into　account.　Three-dimensional　transient　temperature　field　of　the　motor　was　simulated　under　rated　load,　temperature　field　with　different　loads　was　also　computed;　and　some　influence　factors　were　analyzed.　It　was　shown　that　the　temperature　of　stator　and　rotor　increase　rapidly　in　the　beginning,　and　then　the　rising　trend　slow　down　until　reaching　the　stable　state.　In　the　whole　process,　the　rotor　temperature　is　higher　than　the　stator　temperature　all　the　time,　and　the　maximum　temperature　point　is　around　the　axial　center　of　the　rotor　bar.　The　axial　temperature　difference　of　the　rotor　core　is　larger　than　that　of　the　stator　core　while　the　radial　temperature　difference　of　the　stator　core　is　larger　than　that　of　the　rotor　core.　The　temperature　of　air　gap　decreases　linearly　with　the　increase　of　the　thickness,　and　the　thermal　insulation　effect　of　air　gap　is　so　strong　that　it　makes　the　temperature　difference　of　stator　and　rotor　obvious.　The　motor　temperature　grows　with　the　increase　of　load.　There　is　no　linear　relation　between　load　and　temperature.　The　higher　the　wings　of　shell,　the　lower　motor　temperature　is,　whereas　the　descend　tendency　slows　down;　Using　cast　copper　instead　of　cast　aluminum　as　rotor　bars　and　end　rings　can　reduce　the　temperature　of　rotor　effectively.　©　2010　Chinese　Society　for　Electrical　Engineering.