The superconducting YBa2Cu3O7-x thin films were prepared by an in-situ DC sputtering system. The superconducting transition of the films in magnetic fields, applied parallel to the c-axis, was studied experimentally. Arrhenius plots of the resistivity data have shown that the dissipative flux motion of these samples could be explained by the thermally activated mechanism. In addition, we also found that the film on MgO substrate reveals a linear I-V curve, while the film on SrTiO3 substrate shows a nonlinear behavior. The relation between the activation energy and I-V behavior of the films on different substrates is also discussed.