The Ta2O5 thin film is one of the most important high refractive materials in the range from visible to near infrared. This paper researched the optical band gap of the Ta2O5 thin film which was deposited by the Ion Beam Sputtering (IBS). The optical band gap was characterized by the Cody-Lorentz dispersion model. Particularly, the correlations of the band gap and the Urbach with technological parameters were studied respectively. The results show that when the confidence probability is over 95%, the technological parameters are ranked due to their influence coefficients on the band gap as follows: oxygen flow, substrate temperature, and ion beam voltage. Accordingly due to those on the Urbach, the technological parameters are ranked as substrate temperature and oxygen flow. The result provides a method for choosing the key technological parameters to increase the band gap width and reduce the Urbach energy width simultaneously of the Ta2O5 thin film used in the areas of the ultra-low loss thin film and high laser-induced damage threshold thin film.