This　paper　analyzes　the　influence　of　sodium　phosphate　salts　with　different　chain　lengths　as　depressants　on　the　flotation　behavior　of　magnesite　and　dolomite　through　single　mineral　flotation　test,　contact　angle　test,　and　theoretical　analysis.　Flotation　tests　show　that　depressants　should　be　added　for　the　flotation　separation　of　magnesite　and　dolomite.　The　inhibition　of　sodium　phosphate　salts　on　dolomite　is　significantly　stronger　than　magnesite,　and　the　flotation　difference　of　minerals　is　affected　by　the　chain　length　of　phosphate　depressants.　The　order　of　flotation　separation　enhancement　of　different　sodium　phosphate　depressants　is　sodium　hexametaphosphate　approximate　to　sodium　tetrapolyphosphate　＞　sodium　tripolyphosphate　＞　sodium　pyrophosphate.　This　result　could　also　be　supported　by　the　contact　angle　measurement.