The effective potential to describe interactions between the calcium ion and methanol molecule was derived from a potential energy surface. The energy surface was constructed from more than 10 000 points obtained from ab initio calculations, performed at the MP2/6-31G(d,p) level using Gaussian98. The derived effective potential and the Palinkas-Hawlicka-Heinzinger methanol model were employed in the molecular dynamics (MD) simulation of 0.25 M CaCl2 solution in methanol at 298 K. Average distances between ions and the methanol sites-oxygen and carbon atoms-obtained from MD simulation agreed excellently with the X-ray data. The coordination number of the cation, greater as compared with the experimental results, is in accord with its concentration dependence.