The pseudo-binary alloys (PbTe)(1-x)-(SnTe)(x) (0 less than or equal to x less than or equal to 0.4) doped with 0.02 mol% Ag concentration were prepared by spark plasma sintering (SPS). It was observed that the temperature at which the figures of merit Z reach the maximal increases with the mole fraction x, the materials with this temperature dependence of Z values can be used to prepare functionally graded thermoelectric material (FGM). The property of the FGM prepared by SPS is significantly improved as compared with those of any monolithic materials (PbTe)(1-x)-(SnTe)(x) concerned, the maximal power output 12.0 (mW.g(-1)) from calculation and 9.2(mW.g(-1)) from measurement for the FGM are all approximate twice as much as those of the monolithic alloy (PbTe)(0.8)-(SnTe)(0.2), and about 5 times those of (PbTe)(0.6)-(SnTe)(0.4) at the same applied circumstances.