The partition function for liquid water is developed according to the transient state theory of significant liquid structure proposed by Pak, Ahn and Chang. This theory assumes that the molecules may possess solid-like, transient and gas-like degrees of freedom in liquid state. Although liquid water has several special properties, for example, minimum molar volume at 4^{circ}C$, the general theory of liquid can be applied successfully. The theoretically calculated values for thermodynamic properties at the liquid temperature range and for the critical properties are in good agreement with the observed values.