To describe the behavior of liquid state by hole theory, Flory's combinatorial factor used in the partition function of the hole theory is modified in a general form by assuming that unit segment of chain molecule can occupy more than one unit cell or lattice. From this combinatorial factor and free volume expression, a new equation of state is derived, and is used to calculate the PVT behaviors of 10 pure low molecular weight liquid systems. In addition, the PVT behavior of carbontetrachloride/cyclohexane binary system is calculated. Good agreements between the theory and experimental data are obtained.