Phase equilibrium calculation involving mixtures of very many components requires significant amounts of computation time. In this paper we considered the description of such mixtures as a collection of discrete components and a continuum distribution of species represented by the beta distribution function. Calculations are performed using the method of continuous thermodynamics and the Soave-Redlich-Kwong equation of state. Comparisons were made with the pseudocomponent method and gamma distribution function. The results showed that continuous thermodynamics with beta distribution function leads to better prediction of phase equilibria and shorter computing time compared to pseudocomponents. And more reasonable results were obtained by this method because of the flexibility of beta distribution function.