The resonant elastic scattering O-16(alpha,alpha)O-16 at near 3.045 MeV is a very powerful tool For determining the oxygen concentration in oxide films. The resonance yield can be transformed into the stoichiometric ratio of oxygen to Ba-Ti as a function of the probed depth. By means of the resonance yield, we can obtain the oxygen concentration in BaTiO3 films. In this work the method was used to analyze the oxygen concentration of the BaTiO3 films deposited by pulsed laser deposition (PLD) at different oxygen ambience. Our experimental results demonstrate that the oxygen concentration in the films deposited by PLD is homogeneous, and the effect of oxygen pressure in the process of deposition on the oxygen concentration in the films is very significant. It is shown in our experiment that 20 Pa is the lowest value of oxygen pressure for forming optimum BaTiO3 films by the PLD method.