The　axial　and　radial　distributions　of　the　local　particle　velocities　at　different　radial　positions　on　various　axial　levels　along　the　downer-column　were　measured　by　using　a　PV-4A　fiber-optic　particle　velocity　probe　in　a　half-column　downer　of　2　m　high　and　φ30　mm　I.D.,　and　the　effects　of　operation　conditions　and　spouted　positions　on　the　local　particle　velocities　were　also　investigated.　Then　the　radial　particle　velocity　distributions　of　binary　particle　mixture,　formed　by　respectively　and　simultaneously　injecting　fine-FCC　catalysts　and　coarse-glass　beads　in　downers,　were　examined　at　different　composition　ratios　of　FCC　catalysts　to　glass　beads.　Finally,　based　on　the　concept　of　dimensionless　local　particle　velocities　the　new　correlations　for　predicting　the　local　particle　velocity　distributions　of　FCC　catalysts　and　glass　beads　were　developed　by　regressing　experimental　data　from　literatures　and　this　study.　Results　show　that　the　radial　distributions　of　local　particle　velocities　vary　significantly　with　the　particle　properties,　and　for　binary　particle　mixture,　the　radial　distributions　are　more　uniform　as　compared　with　those　of　only　FCC　catalysts　and　the　double-peaked　distribution　characteristics　of　particle　velocity　profiles　become　more　obvious　with　the　increase　of　superficial　gas　velocities,　since　in　this　case　fine　particles　mixed　by　injecting　coarse　particles　will　result　in　the　variation　of　gas-solids　dynamic　mechanism　and　the　smoothness　of　particle　velocity　distributions　in　dowers.