Gain characteristics of waveguide amplifiers based on SU-8 2005 doped with NaYF₄∶18％Yb³⁺, 10％Er³⁺ nanocrystals (NCs) at 1.55μmm wavelength are investigated through numerical simulations. NaYF₄∶18％Yb³⁺,10％ Er³⁺ NCs are doped into SU-8 2005 polymer matrix as the core of the polymer waveguide, and the P(MMA-GMA) polymer is used as the top cladding. The absorption spectrum and photoluminescence spectrum of the NCs are measured and analyzed. The Judd- Ofelt parameters are achieved by means of Judd- Ofelt theory: Ω₂ = 6.302 × 10^-20 cm², Ω₄ = 0.69 × 10^-20 cm², Ω₆ = 7.572 × 10^-20 cm². The gain characteristics of the waveguide amplifier at 1.55 μm wavelength are simulated by combining the power propagation equations as well as the atomic rate equations. The gain curves have the saturation effects. The maximum gain of 9.7 dB with the Er3+ concentration of 7.5 × 10²⁵ m^-3 is obtained. The top cladding of the waveguide amplifier with SU- 8 doped with NaYF₄∶Yb³⁺ , Er³⁺ nanocrystals is P(MMA-GMA), and bottom cladding is SiO₂, respectively. For input signal power of 0.1 mW and 980 nm pump power of 170 mW, a relative optical gain of 3.42 dB/cm at 1550 nm is obtained.