A cubic equation of state is proposed to improve the calculation performance for liquid-phase densities. For the repulsive part, the Scott-I expression developed for hard sphere fluid is adopted and the attractive part proposed by Fuller is combined with the repulsive part. For typical binary systems, both vapor-liquid equilibria and saturated densities of vapor and liquid phases were calculated by the equation of state with the conventional mixing rule. Good agreement is found between calculated and experimental saturated liquid densities, as well as vapor-liquid equilibria, though a discrepancy is found in the calculation of liquid densities by SRK equation of state widely used.