Well　loss　is　a　common　and　complex　accident　in　drilling　engineering.　The　wellbore　temperature　under　lost　circulation　plays　a　very　important　role　on　safe　drilling　and　affects　rheology　of　fluid,　wellbore　pressure,　well-wall　stability,　etc.　At　present,　the　study　on　wellbore　temperature　profile　under　lost　condition　is　quite　limited.　And,　factors　that　have　obvious　impact　on　the　wellbore　temperature　distribution　are　neglected　in　the　existing　heat　transfer　model　under　lost　circulation,　which　reduces　the　accuracy　of　simulated　results.　In　this　paper,　a　wellbore　heat　transfer　model　is　developed　to　predict　the　wellbore　temperature　profile　under　the　condition　of　lost　circulation.　The　effects　of　drilling　fluid　lost　into　zone,　complex　casing　programs,　and　heat　sources　on　wellbore　temperature　under　the　condition　of　lost　circulation　are　fully　considered　in　the　model.　And,　the　model　is　solved　by　iterative　method.　Then,　the　model　is　validated　by　the　measured　temperature　data　and　the　existing　model.　Comparison　results　show　that　the　simulated　results　by　the　model　in　this　paper　are　more　consistent　with　the　true　value　after　considering　these　factors.　Last,　case　study　is　conducted　under　lost　circulation　condition.　Some　meaningful　conclusions　are　listed　below:　(a)　The　annular　fluid　temperature　near　the　wellhead　is　less　than　the　fluid　temperature　inside　the　drill　pipe　under　lost　circulation;　(b)　Different　from　normal　circulation,　there　is　an　inflection　point　on　the　temperature　difference　curve　under　lost　circulation;　(c)　The　number　of　inflection　points　on　the　annular　fluid　temperature　distribution　curve　increases　with　the　increase　of　loss　zone　number;　(d)　Under　the　same　change　of　loss　rate,　flow　rate,　thermal　conductivity　of　formation,　and　heat　capacity　of　fluid,　the　variation　range　of　fluid　temperature　at　bottom-hole　is　greater　than　the　variation　range　of　fluid　temperature　at　wellhead.