Using pure metal Ag, Te, Ge and Sb powders as raw materials, (AgSbTe2)100-x-(GeTe)x (x=8090) (TAGS) are synthesized by vacuum reaction. X-ray diffraction (XRD) analysis results show that after sintering the alloys each have a rhombohedral structure. TAGS power is sintered by hot pressing method. Their phase compositions, crystal structures and morphologies are characterized by XRD and scanning electron microscope analysis methods. Their electric conductivities are measured by direct current method. Their Seebeck coefficients are measured when a temperature difference (T=14℃) is applied along two ends of sample. Through testing the thermoelectric properties of materials, the variations of different performance parameters of the sample are investigated in a temperature range of 30500℃. The results show that the sample is nano crystals and its thermoelectric properties change as the composition changes. We can see that TAGS-80 has a good thermal performance, with ZTmax=1.8 at 530℃.