MLAA-34　is　a　newly　identified　monocytic　leukemia-associated　antigen　that　is　overexpressed　in　acute　monocytic　leukemia　specifically,　thus　providing　a　novel　target　for　the　therapy　of　acute　monocytic　leukemia.　In　this　study,　we　first　expressed　MLAA-34　protein　in　Escherichia　coli　(E.coli)　BL21　(DE3)　cells　and　purified　it　by　nickel　ion　affinity　chromatography　with　high　purity　(＞　90%).　Then,　MLAA-34　was　used　as　antigen　for　biopanning　anti-MLAA-34　single　chain　antibody　fragment　(ScFv)　from　a　fully　human　ScFv　library,　and　a　high　affinity　ScFv　named　MA1　was　selected　by　phage-ELISA.　Finally,　after　expression　of　MA1,　we　found　that　MA1　can　specifically　bind　with　U937　MLAA-34　positive　cells,　and　the　binding　affinity　of　MA1　was　at　the　nanomolar　level.　Furthermore,　inhibition　of　U937　cell　proliferation　indicated　that　the　novel　antibody　MA1　has　the　potential　to　be　used　as　a　therapeutic　agent　for　acute　monocytic　leukemia.