The　gas-lift　pump　has　been　adopted　to　enhance　the　natural　circulation　capability　in　the　type　of　lead-bismuth　alloy　cooled　reactors　such　as　ADS　and　LMFR.　The　natural　circulation　ability　and　the　system　safety　are　obviously　influenced　by　the　two　phase　flow　characteristics　of　liquid　metal-inert　gas.　In　this　study,　the　numerical　research　has　been　performed　to　evaluate　the　natural　circulation　capability　of　lead-bismuth　cooled　ADS　with　gas-lift　pump.　The　drift　flow　theory,　void　fraction　prediction　model　and　friction　pressure　drop　prediction　model　have　been　adopted　in　this　numerical　simulation.　The　effects　of　the　gas　flow　rate,　the　bubble　diameter　and　the　height　of　ascension　pipe　on　natural　circulation　capability　of　gas-lift　pump　have　been　analyzed.　The　results　showed　that　in　bubbly　flow　pattern,　for　a　fixed　value　of　gas　volume　flow　rate,　the　natural　circulation　capability　increased　with　the　decrease　of　the　bubble　diameter.　In　the　bubbly　flow,　slug　flow,　churn　flow　and　annular　flow　pattern,　with　the　gas　volume　flow　rate　increasing,　the　natural　circulation　capability　initially　increased　and　then　declined.　As　the　height　of　ascension　pipe　increased,　the　natural　circulation　flow　rate　went　up.　Besides,　the　flow　parameters　influenced　the　thermal　hydraulic　characteristics　of　the　reactor　core　obviously.　Therefore,　in　the　practical　engineering　application,　the　suitable　gas　volume　flow　rate,　bubble　diameter　and　the　height　of　ascension　pipe　are　important　parameters　to　the　capability　of　natural　circulation　in　lead　bismuth　alloy　loop　of　this　research.　The　present　work　is　helpful　for　revealing　the　law　of　enhancing　the　natural　circulation　capability　by　gas-lift　pump,　and　providing　theoretical　basis　of　the　optimization　design　of　cooling　and　system　safety