Li0.2375+xLa0.5875-xSrxTiO3-LaPO4　fast　ionic　conductor　was　synthesized　by　high　temperature　solid　state　reaction　A.C.　impedance　measurements　show　that　the　system　has　higher　conductivity　in　low　doping　content　of　Sr2+,　but　the　conductivity　goes　down　from　5.78　x　10(-5)　to　3.11　x　10(-7)　S(.)cm(-1)　with　increasing　the　content　of　Sr2+.　The　activation　energy　is　about　20　kJ(.)mol(-1)　in　the　temperature　range　of　25　similar　to　400　degreesC.　X-ray　powder　diffraction　shows　that　the　doping　Sr2+　would　not　affect　the　structure　of　compositions　in　the　system.　The　main　phase　is　Li0.2375+xLa0.5875-xSrxTiO3　perovskite　solid　solution,　LaPO4　as　a　second　phase　can　also　be　found.　With　increasing　the　content　of　Sr2+　(x　＞　0.05),　another　phase　SrTiO3　appears.　IR　measurement　also　indicates　that　the　structure　of　compositions　in　the　system　would　not　be　affected　by　Sr2+　doping.　The　decomposition　voltage　of　Li0.2375+xLa0.5875-xSrxTiO3-LaPO4　remain　unchanged　(1.5　V).