Er3+-doped silica microspheres with smooth surface are fabricated through surface tension induced by heating and fusing a single tapered silica fiber between two discharge electrodes. The tapered fiber is dipped with quantitative erbium nitrate solution. Single mode laser of 976 nm is coupled into microsphere through near-field coupling by evanescent wave from biconical tapered fiber, exciting high power density whispering gallery modes (WGM) in the microsphere. And downconversion emission spectrum of C+L band of optical communication is obtained, which is emitted from stimulated Er3+ distributing all over the surface of microsphere. Single-longitudinal-mode and multi-longitudinal-mode lasers are also measured at around 1555 nm and 1600 nm. The diameters of the microspheres tested in our experiment are between 70~150 μm, and the concentration of the erbium nitrate solution is about 10-5～10-4 mol/mL. The methods of microsphere fabrication and rare earth doping are simple and practicable for fast measurement of the luminescence of rare earth doped materials.