BaO-Nd2O3-Sm2O3-TiO2(BNST) thin films were prepared by RF magnetron sputtering technique on Pt/Ti/ LaAlO3 (100) substrates, then the films were annealed with different annealing temperature in air to improve crystallization. The influence of the annealing temperature on the BNST thin films structure, morphology and dielectric properties was studied by XRD, AFM and LCR. The results showed that the crystalline degree, the grain size and the dielectric constant increase with the rise of annealing temperature. The minimum dielectric loss and surface roughness was achieved at 850 ℃. The dielectric constant reached to 37, and the dielectric dissipation was less than 1.2‰ at frequency of 100 kHz.