In this study, an intermediate temperature ionic conductor, $Ce_{0.95}Eu_{0.05}P_2O_7$, was prepared by solid state reaction. The variation of conductivities with the pressure $pH_2O$ or time were studied. The highest conductivity of $Ce_{0.95}Eu_{0.05}P_2O_7$ sample was observed in dry air atmosphere at $300^{circ}C$ to be $1.1{ imes}10^{-4}S{cdot}cm^{-1}$ and in wet air atmosphere ($pH_2O=7.4{ imes}10^3Pa$) at $100^{circ}C$ to be $1.4{ imes}10^{-3}S{cdot}cm^{-1}$, respectively. The log ${sigma}$ ~ log ($pO_2$) plot result indicated that $Ce_{0.95}Eu_{0.05}P_2O_7$ was almost a pure ionic conductor under high oxygen partial pressure and a mixed conductor of ion and electron under low oxygen partial pressure.