In　this　study,　the　effects　of　calcium　ions　on　the　flotation　of　malachite　with　octyl　hydroxamate　collector　has　been　investigated　using　micro-flotation,　zeta　potential,　contact　angle,　adsorption,　and　particle　size　measurements.　Although　the　adsorption　amount　of　collector　and　the　hydrophobicity　of　malachite　surface　were　not　influenced　by　the　addition　of　1　x　10(-2)　mol/L　CaCl2　at　the　optimized　flotation　pH　9,　it　was　found　that　the　malachite　flotation　recovery　was　enhanced　by　the　addition　of　CaCl2　in　the　pH　range　of　6-11.　In　the　presence　of　CaCl2,　energy　barrier　between　the　malachite　particles　and　the　bubbles　were　lower,　leading　to　the　aggregation　of　malachite　particles,　and　the　enhanced　malachite　recovery.　However,　at　pH　＞　11,　the　formation　of　Ca(OH)(+)　and　Ca(OH)(2)　species　on　malachite　surface　inhibited　its　flotation.