A stable and accurate inverse method for extracting potential from spectroscopic data studied. The method is based on the Tikhonov regularization method to overcome the possible instability of nonlinear inverse problems using a priori smooth properties of the potential energy surface. The merit of this method is to treat the potential as continuous functions of the intermolecular coordinates instead of the conventional parameter fitting of restricted potential forms. Numerical study for the Ar-Ar show that from spectroscopic data the exact potential has been recovered whole region and the discrepancies by the dispersion force observed at the large distance between the exact and Morse potential or from RKR method can be eliminated by this method.