We have investigated the dispersion of charged single-wall carbon nanotube bundles by using density functional theory. We obtained the variation of equilibrium spacing between tubes as a function of charge density for the (4, 4) and (7, 0) tubes with different charge signs and the minimum charge density to cause separation. We also calculated the cohesive energies between two charged tubes as a function of interwall spacing and found that extra energy supply can promote separation of nanotube bundle. Our results are in good agreement with the experimental values.