The ternary Ag0.405Sb0.532Te alloy was prepared by spark plasma sintering, and its transport properties involving Seebeck coefficients, electrical and thermal conductivities were evaluated. The results reveal that the electrical conductivity mildly decreases from 7.6′104 S·m-1 to 6.6′104 S·m-1 when the temperature increases from 316 K, to 548 K. Above 438 K, the thermal conductivity gradually increases with the increase of the temperature, and below 438 K, a relative stable value of about 0.86 W·K-1·m-1 is obtained. The maximum thermoelectric figure of merit ZT is up to 0.65 at 548 K, a little higher than 0.61 of the ternary alloy Ag0.365Sb0.558Te. The thermoelectric properties have been improvement compared with the Ag-doped AgxBi0.5Sb1.5-xTe3 alloys (x=0-0.4). The action mechanism of the second phase Ag-Sb-Te ternary alloy precipitated in the AgxBi0.5Sb1.5-xTe3 alloys has been re-discussed