A molecular thermodynamic model based on the theory of melting point depression, the Adam-Gibbs configurational entropy model, and the modified lattice-fluid model was developed to interpret ionic conductivities of solid polymer electrolytes with various pressures. A new configurational entropy, S was introduced in this model. Quantitative descriptions according to the proposed model agreed with the experimental data for the given systems. Our results showed that a eutectic point moves toward higher melting temperatures, whereas a lower weight fraction of salt and the ionic conductivity significantly decrease with pressure.