To　complete　high　quantity　arsenic　disposal　process　in　groundwater,　after　As(III)　oxidized　into　As(V)　by　biological　filter　effectively,　the　optimal　conditions　for　compound　coagulants　to　remove　As(V)　were　conducted.　Under　the　condition　of　As(V)　in　the　raw　water　of　2　mg/L,　iron-aluminum　compound　coagulants　were　better　than　the　single　coagulant　such　as　the　iron　salt　or　the　aluminum　salt　for　the　removal　of　As(V),　which　could　save　more　than　50%　adding.　Besides,　compound　coagulants　improved　the　absorption　and　sedimentation　performance　for　As(V)　and　sedimentation　performance　for　floc.　For　the　trace　of　As(V)　in　the　effluent,　Al　played　more　important　role　in　As　removal　and　cross　interaction　for　the　two　coagulants　was　also　prominent.　When　combined　the　iron　trichloride　(5　mg/L)　with　the　polymer　aluminum　sulfate　(3　mg/L),　the　effect　of　arsenic　removal　was　the　best.　The　optimal　conditions　for　the　compound　coagulants　show　that　when　pH　is　6.00-7.00　and　turbidity　is　more　than　30　NTU　or　less　than　10　NTU,　the　efficiency　of　compound　coagulants　for　removal　of　the　arsenic　is　the　highest,　which　is　stable　to　meet　the　request　of　the　national　hygienic　standards　for　drinking　water(10　μg/L).