Al element was substituted for In in the (In2Te3)0.09 (SnTe)0.91 compound with the same molar fraction and (In2Te3)0.09 (SnTe)0.91 and (In1.9Al0.1Te3)0.09(SnTe)0.91 compounds were prepared by spark plasma sintering. The microstructure and the thermoelectric property of the compounds were investigated. Results show that although the Seebeck coefficient of the sample is almost unchanged after Al doping, the electrical conductivity increases to 1×105 W-1·m-1 at 321 K and to 2.3×105 W-1·m-1 at 705 K, being at least 2.4~3 times that of Al free (In2Te3)0.09(SnTe)0.91 compound, and the lattice thermal conductivity is significantly decreased. The highest ZT value of 0.4 is obtained at 693 K, which is approximately 2 times as large as that of the Al-free (In2Te3)0.09(SnTe)0.91 compound at the same temperature.