LiSn2P3O12 has been prepared using mechanochemical milling method and sintered at 700 °C, 800 °C, 900 °C and 1000 °C for 8 hours. All samples sintered up to 900 °C show a rhombohedral structure. However, the sample sintered at 1000 °C possessed a monoclinic structure. This is attributed to the rotation of skeleton LiSn2P3O12 as indicated by the change in the a and c parameters of the sample. The sample sintered at 700 °C shows the highest bulk conductivity of 1.65 × 10-6 S cm-1 and the lowest bulk activation energy of 0.09 eV. The grain boundary activation energy of the samples decreases with increase in sintering temperature due to enhancement in grain contacts.