On the basis of thermodynamic perturbation theory, an analytical equation of state has been obtained, as well as analytical expressions for the internal energy and Helmholtz energy, applicable in the case of strongly compressed gas at a pressure of the order of hundreds of kilobars. The expressions obtained are universal. i. e. , do not depend on the form of the intermolecular potential. Specific calculations are performed for Lennard-Jones and exp-6 potentials. The results of the calculations are in good agreement with the thermodynamic data obtained by the Monte Carlo method.