The surface tension (] and the surface density thickness t of nuclear matter have been calculated in the Fermi-gas model, the nucleons moving in a self-made shell model potential with a realistic slope and velocity dependence (parameters a and. (J) where the total energy E of the nucleus is a function of the mass number A, the Fermi momentum kf, and the surface area S. This definition is practically in accordance with the definition given by Swiatecld and other authors [3,6,7,9]