A series of LiAlO2-Li3PO4 solid state lithium ion electrolyte materials were prepared through solid-phase reaction. The influences of experimental operating parameters such as the Molar ratio of materials, and the sintering temperature on the characteristics of the sintered samples were investigated. The results showed that, at 1∶1 stoichiometric ratio of LiAlO2 and Li3PO4, the specimens sintered at 1 000 ℃ consisted of γ-LiAlO2 flakes and γ-Li3PO4 spheres, and the sizes of particles ranged from 0.5 to 1 μm. When the stoichiometric ratio of LiAlO2 and Li3PO4 was 1∶3, the specimens sintered at 1 000 ℃ consisted of mainly Al doped spherical γ-Li3PO4 solid solution and its ionic conductivity was 6.4×10-5 S/cm. It indicated that Al doping could effectively improve the ionic conductivity of Li3PO4 inorganic solid electrolyte. When the Al doped specimens were sintered at 1 100 ℃, the ionic conductivity decreased. The results of cyclic voltammetry showed that the Al doped γ-Li3PO4 solid electrolyte materials had a good electrochemical reversibility in saturated LiNO3 solution, and an electrochemical window of 1.5V was observed.