The dc conductivity and dielectric parameters of glassy system of a-Se70Te30-x Sn (x) (x = 0, 2, 4, 6, 8 and 10) glasses have been investigated. Frequency and temperature dependence of dielectric constants (epsilon') and dielectric loss (epsilon'') are studied in the frequency range 120-100 kHz and temperature range 300-390 K. Dielectric dispersion is observed when Tin (Sn) is incorporated to a-Se-Te system in the entire temperature range. These results explain that the dc conduction loss is dominated in the present system. From dc conductivity studies it is observed that the dc conductivity and activation energy increases with increasing tin concentration in the present system.