Intracloud lightning discharges are simulated in 12.5 m (fine) and 250 m (coarse) resolution for 2-dimensional domain by using an improved Stochastic Lightning Model. Simulation results indicate that the bi-level branched channel structure, horizontal extending ranges and maximum vertical electric field changes obtained from fine resolution lightning model are in better agreement with previously observed data than those from coarser model. The IC flash channels from fine lightning model have the fractal feature with fractal dimension of 1.43, and propagation tendency is dependent on the potential distribution. In addition, fine resolution lightning modeling shows that after IC flash initiation at the boundary between positive and negative potential zones, potential wells attract the leaders of opposite polarity into the central area and prevent their outward expansion. Leaders can propagate throughout regions of net charge of the opposite polarity, but they avoid the isolated charge areas of the same polarity.