With　the　development　of　mineral　dressing　techniques,　some　sulfide　lead–zinc　tailings　have　become　valuable　because　the　lead　and　zinc　can　be　recovered　through　secondary　flotation.　However,　owing　to　long-term　open　storage,　the　surfaces　of　lead–zinc　sulfide　minerals　become　oxidized,　and　their　floatability　is　significantly　reduced.　In　this　study,　the　effects　of　oxidation　on　the　floatability　and　flotation　separation　of　galena　and　sphalerite　ore　of　different　grain　sizes　were　systematically　investigated　via　microflotation　and　surface　detection　analysis　techniques.　The　microflotation　results　indicated　that　surface　oxidation　reduced　the　floatability　of　galena　and　sphalerite　and　increased　the　difficulty　of　flotation　separation　between　them.　Within　the　grain　size　range,　a　larger　grain　size　corresponded　to　a　more　obvious　inhibition　effect　and　more　difficult　separation　of　galena　and　sphalerite　after　oxidation.　This　was　mainly　due　to　the　generation　of　hydrophilic　oxidized　substances　on　the　surfaces　of　the　minerals　after　oxidation,　which　hindered　the　adsorption　of　the　collector.　Ultrasonic　cleaning　can　remove　the　oxides　on　the　surface　of　lead　and　zinc　sulfide　ores　and　restore　their　floatability,　while　improving　the　flotation　separation.　©　The　Minerals,　Metals　&　Materials　Society　2025.