Colossal　magnetoresistance　material　La1-xCaxMnO3　polycrystalline　ceramics　have　been　prepared　by　conventional　solid-state　reaction　method　with　the　x　=　0.15-0.5.　The　R-T　results　show　that　the　sample　with　x　=　0.33　possesses　the　best　insulator-mental　transition　temperature.　The　Tc　of　La0.67　Ca0.33　MnO3　has　been　measured　by　the　M-T　curve,　which　is　near　the　temperature　of　265K.　Then　we　doped　2-15wt%　silver　into　La0.67　Ca0.33　MnO3,　and　got　the　results　that　4wt%　Ag-doping　La0.67　Ca0.33　MnO3　shows　the　best　insulator-metal　transition　temperature.　And　the　MR　is　much　higher　than　the　one　of　La0.67　Ca0.33　MnO3　without　silver.　The　results　of　XRD　and　SEM　show　that　the　silver　has　been　doped　into　the　grain　boundaries　and　holes　but　not　the　crystal　lattices.　The　mechanism　of　Ag-doping　has　been　analyzed　preliminarily.