Yb3+ doped silica glass preforms are fabricated by MCVD process combined with the solution doping technique.Absorption and emission spectra of preforms with various Yb3+ concentrations are investigated.The intensities of absorption and emission increase with increasing of solution concentrations of YbCl3.The maximum YbCl3 solution concentration can be doped into core layer of preform without compromising vitrification is 0.057 mol/L.