We　have　prepared　(Sr1-xMgx)(Sn0.5Ti0.5)O3,　(X　=　0.00,　0.25,　0.50,　0.75)　samples　by　the　solid　state　reaction　method　and　studied　the　structural,　optical,　electrical　modulus　and　the　other　dielectric　properties　of　the　samples　with　respect　to　variation　in　frequencies　(1　x　109　to　2　x　109　Hz)　using　Impedance　Analyzer.　This　study　suggests　that　the　XRD　patterns　of　the　samples　have　shown　that　this　possesses　cubic　perovskite　structure　in　space　group　Pm-3m　and　scanning　electron　microscope　was　used　to　analyze　the　grain　size　distribution　and　porosity　of　the　ceramic.　The　dielectric　properties　of　these　materials　were　strongly　dependent　upon　on　concentration　X　as　well　as　amount　of　frequencies.　The　existence　of　metal　oxygen　bonds　of　Sr-Ti-O　was　verified　by　Fourier　Transform　Infra　Red　(FTIR)　spectrum　at　540　cm-1.　The　highest　PL　intensity　of　716.38　that　exhibits　the　green　emission　(508.5　nm)　was　obtained　for　the　composition　of　(Sr0.25Mg0.75)(Sn0.5Ti0.5)O3.　AC　conductivity　slowly　decreases　with　increasing　Mg　substitution　and　also　the　sample　(Sr0.25Mg0.75)(Sn0.5Ti0.5)O3　having　the　lowest　(constant)　value　of　conductivity　at　1　GHz-2GHz.