By means of a Langevin dynamic simulation we studied the current-voltage characteristics of a two-dimensional (2D) Josephson-coupled lattice as a model high-Tc superconducting film. The result illustrates qualitative features of non-Ohmic power-law scaling behaviors observed in transport measurements, including striking effects of applied magnetic fields. We thereby suggest that the Kosterlitz-Thouless transition associated with 2D vortex-antivortex pairs may dominate over the resistive transition in weak magnetic fields H/Hc
2 ≪C 1. Through a simple theoretical estimate, we also show that the KT model illustrates the thickness-dependence of resistive transition temperature and electric field effect in ultra-thin YBa2Cu3O7−x films.