The　gas　lift　pump　has　been　used　in　the　development　of　an　Accelerator　Driven　System　(ADS)　nuclear　reactor　instead　of　mechanical　pumps　due　to　its　simple　mechanical　structure.　The　two　phase　flow　of　Lead　Bismuth　eutectic　(LBE)-inert　gas　in　rising　pipe　could　remarkably　increase　natural　circulation　capacity.　This　study　aims　to　evaluate　the　performance　of　the　gas　lift　pump　and　to　conduct　the　relevant　parametric　study.　As　a　result,　the　Natural　Circulation　Capability　Loop　(NCCL)　test　facility　was　designed　and　constructed.　The　height　of　the　experimental　loop　is　4.5m　and　the　rising　height　is　3.5　m.　The　maximum　temperature　of　the　loop　is　500　degrees　C.　The　experiments　about　the　gas　lift　pump　in　LBE　were　performed　with　risers　of　three　different　heights.　The　results　showed　that　the　LBE　mass　flow　rate　increases　rapidly　with　an　increase　of　argon　flow　rate　when　it　is　less　than　300　NL/h.　When　the　argon　flow　rate　is　larger　than　300　NL/h,　the　growth　of　the　LBE　mass　flow　rate　is　reduced.　The　LBE　mass　flow　rate　increased　process　is　accompanied　by　the　transformation　of　the　flow　pattern.　The　variation　trend　of　the　LBE　flow　rate　is　consistent　with　the　trend　of　the　void　friction　in　the　riser.　Under　the　same　amount　of　argon　gas　injection,　the　LBE　circulation　ability　increases　as　the　height　of　the　riser　increased.　Based　on　the　experimental　data　and　drift-flow　model　of　Zuber　and　Findlay,　a　new　correlation　of　the　void　fraction　is　obtained　and　the　relative　error　between　the　calculated　and　the　experimental　value　is　within　30%.　The　purpose　of　this　study　is　to　reveal　the　enhancement　mechanism　of　the　natural　circulation　capacity　of　gas　lift　pump　and　to　provide　experimental　data　and　model　support　for　the　design　of　ADS　in　China.