It　is　of　significant　importance　to　predict　the　location　of　phase　transition　during　CO2leakage.　A　coupled　computation　method　was　established　to　describe　CO2phase　transition　during　leakage　based　on　non-isothermal　flow　and　phase　transition　of　CO2along　a　leaky　pathway,　in　which　the　Span-Wagner　equation　and　the　equivalent　specific　heat　method　were　combined.　The　influence　of　the　Joule-Thomson　effect,　viscous　dissipation　effects　and　heat　transfer　effects　on　CO2leakage　were　investigated.　Major　factors　and　their　relative　effects　on　phase　transition　during　CO2leakage　were　elucidated.　The　results　show　that　although　the　Joule-Thomson　effect　and　the　viscous　dissipation　effect　have　opposite　effects　on　temperature　distribution　along　the　leaky　pathway,　both　factors　enable　the　location　of　CO2phase　transition　moving　towards　deeper　subsurface.　The　increase　of　heat　exchange　between　the　leaky　pathway　and　its　surroundings　decreases　the　temperature　of　the　leaky　pathway.　The　combination　of　the　Joule-Thomson　effect　and　heat　exchange　further　decreases　the　temperature　of　the　leaky　pathway,　which　leads　the　CO2phase　transition　location　moving　towards　shallower　subsurface,　and　the　flowrate　at　the　outlet　of　the　leaky　pathway　increases.　©,　2015,　Zhejiang　University.　All　right　reserved.