The transparent tin oxide thin films with an average transmissivity larger than 90% are fabricated on the glass substrates by the spin-coating method with SnCl4·5H2O as the source material of the precursor solution. The research results show that, the plasma pre-treatment to glass substrates is helpful to improve the surface quality of the tin oxide films and the best surface quality is obtained when the plasma treatment power is 25 W. The increase of the annealing temperature kept below 500 ℃ can not only reduce the residue of organic components but also increase the thin film band gap under the condition that the thin film phase compositions do not change. When the annealing temperature increases to 500 ℃, the thin film phase composition changes from non-crystalline to polycrystalline.