A　fiber-taper-microsphere-coupled　system　was　used　to　research　the　characteristics　of　laser　oscillation　and　upconversion　luminescence　of　Yb3+:Er3+　co-doped　phosphosilicate　(YECP)　microspheres.　The　YECP　microspheres　were　fabricated　by　melting　the　end　of　phosphosilicate　filaments.　Single-and　multimode　laser　oscillation　at　1535-1565　nm　within　the　C-band　were　obtained.　In　addition,　the　output　power　of　the　single-mode　laser　at　1545.5　nm　can　be　as　high　as　48.98　W,　which　was　achieved　under　pump　power　of　9.63　mW,　and　the　side-mode　suppression　ratio　was　51.49　dB.　Upconversion　fluorescence　of　Er3+　at　521,　532,　and　544　nm　also　were　measured,　and　the　pump　power　dependence　was　studied.　The　fluorescence　intensity　was　lower　than　that　of　Yb3+:Er3+　co-doped　silica　and　oxyfluoride　glass　ceramic　microspheres.　Moreover,　the　physical　mechanism　of　upconversion　suppression　and　laser　oscillation　enhancement　observed　in　our　experiment　was　presented,　which　is　beneficial　to　the　preparation　of　rare-earth-doped　microcavity　lasers.　(C)　2014　Optical　Society　of　America