The present work studies possibilities for description of surface characteristics of alkali series in terms of the density functional theory. The metal surface is considered in the model of a metal in which the positive charges are replaced by a uniform charge background of density. The main objective was to build the optimal type of new trial functions for electron number density distribution, which would take into account the Friedel oscillations, and to calculate the variational parameters of those functions. Self-consistent calculation of the surface energy of alkali metals was carried out taking into account the gradient corrections for inhomogeneity of electron gas in the surface region for the kinetic energy. In this paper, we determined surface characteristics, such as the work of exit and the potential barrier height. The effective potentials for selected alkali metals were constructed.