The current–voltage characteristics (CVC) of YBa2Cu3O7–δ epitaxial films were determined at temperatures and magnetic fields covering the vortex‐liquid region. Using functional fitting and scaling method, we derived the temperature and magnetic field dependences of the pinning potential U0(T,H) and critical current density Jc(T,H), and current, temperature and magnetic field dependences of the effective pinning potential Ueff(H,T,J) from the CVC. It is shown that the nonlinear resistance region of the vortex‐liquid phase displays a process from vortex plastic motion to free flow with the dynamic exponent changing from –0.5 to 0.