Gain characteristics of polymer waveguide amplifiers based on NaYF4∶ Yb3+,Er3+ nanocrystals(NCs)were investigated through numerical simulations.NaYF4∶ 18%Yb3+,10%Er3+ NCs were doped into SU-8 2005 polymer matrix as the core of the polymer waveguide.The absorption spectrum and photoluminescence spectrum of the NCs were recorded and analyzed.The Judd-Ofelt parameters were achieved by means of Judd-Ofelt theory: Ω2=6.302×l0-20Ccm2,Ω4=0.69×l0-20cm2,Ω6=7.572×l0-20Cm2.We combined the atomic rate equations with power propagation equations to simulate the gain characteristics of the waveguide amplifier at 0.54μm wavelength.The gain curves had the saturation effects.The maximum gain for the 4cm waveguide with the Er3+ concentration of~7.5 x 1024m-3 we obtained was~5.ldB.