The single-phase Sb-doped n-type Ba8Ga16-xSbxGe30 compounds were synthesized by melting reaction combined with spark plasma sintering. Influences of substituting Sb for Ga on the thermoelectric properties of the compounds were investigated. The results indicate that with the increase of Sb substitution fraction the Seebeck coefficient is decreased gradually, and the temperature which corresponds to the peak value of Seebeck coefficient moves to low-temperature. The electrical conductivity of the compounds increases at first and then decreases with the increase of x; when x=2, it reaches maximum. Substituting Sb for Ga has a great influence on the thermal properties of the compounds. Both the thermal conductivity and lattice thermal conductivity decrease in various degrees. Of all n-type Ba8Ga16-xSbxGe30 compounds, the compound Ba8Ga14Sb2Ge30 has the greatest ZT value, the maximal value of which reaches 1.1 at about 950 K.