This paper proposes a waveguide type optical amplifier which is constructed in 1.3 at.% Nd doped yttrium gallium garnet thin films deposited on yttrium aluminum garnet substrates by using RF sputtering . The crystalline thin film with a satisfactory stoichiometric composition is obtained by annealing at 1000 after depositing at 600. The spectral properties and the optical amplification characteristics of the thin film waveguide are measured. Optical propagation loss of 2.2 dB/cm is achieved at the wavelength of 1061.5 nm. Absorption peak of the thin film is located at 808 nm, and fluorescence peaks at about 1.06 µm and 1.3 µm suggest the possibility of optical amplification. For the wavelength of 1061.5 nm, a maximum gain of 4.4 dB and a S/N ratio of 12.6 dB are obtained at a signal power of 10 µW and the pump power of about 14 mW. The pump efficiency is more than 0.3 dB/mW.