A charge distribution method to solve the linearized Poisson-Boltzmann equation numerically through use of the finite difference method is proposed. The molecules are mapped by 1 and 0.25 Angstrom grid systems. Each atom is modeled as a point charge and a weighted sum of point charge of every atom that is within its van der Waals radius with a grid point is assigned to the grid point. Depending on a charge distribution factor determined, the charge/grid (q/g) ratio calculated for every grid point inside a molecule can be fixed to a certain value. A grid size of the 1 Angstrom grid is often fixed for mapping a small or large molecular system. Solvation energies for a group of small molecules calculated by the method are comparable with those calculated by other methods and the grid energy calculated by the method is also reduced.