Polycrystalline AgPb18+xSbTe20 compounds with different Pb contents (x=1-4) were prepared by melting method and spark plasma sintering techniques. The crystal structure and chemical composition were determined by XRD and EPMA. The thermal conductivity, electrical conductivity and Seebeck coefficient were measured in the temperature range of 300-800K. The dimensionless thermoelectric figure of merit (ZT) of AgPb18+xSbTe20 (x=1-4) increases in the whole temperature range of 300-750K which is different to the pure lead telluride compound. The maximum ZT value reaches 1.03 at 800K.