Sb element was substituted for Ga in the Ga2Te3 alloy with the same molar fraction and Ga1.9Sb 0.1Te3 alloy was prepared by spark plasma sintering. The microstructure and the thermoelectric (TE) property of the alloy were investigated. Results show that after Se doping the Seebeck coefficient of the sample is about 130-240 mV/K, much lower than that of single crystal Ga2Te3, and the electrical conductivity decreases from 3600 to 1740 W-1·m-1 with temperature elevation to 649 K, being at least 16 times higher than that of single crystal Ga2Te3 at the corresponding temperature. The thermal conductivity increases by about 25% after Sb doping. The maximum TE figure of merit (ZT) value of 0.1 is obtained at 649 K, which is approximately 3 times as large as that of single crystal Ga2Te3 at the corresponding temperature