In general, (GeTe)_n(Bi₂Te₃)_m compounds in GeTe-Bi₂Te₃ pseudo-binary system possess a relatively low thermal conductivity, however, the thermoelectric properties of these compounds have not been evaluated systematically. In this study, a series of single-phase (GeTe)_nBi₂Te₃ (n=10, 11, 12, 13, 14) compounds were prepared by a melting-quenching-annealing process combined with spark plasma sintering. The phase compositions and thermoelectrical properties of these samples were characterized. It is found that doping with Bi₂Te₃ intensifies the phonon scattering and significantly reduces the lattice thermal conductivities of these samples, producing a low total thermal conductivity of 1.63 W?m ^-1?K ^-1 at 723 K for (GeTe)₁₃Bi₂Te₃ compound. Moreover, the effective mass of these compounds is enhanced through adjustment of the relative amount of Bi₂Te₃ and GeTe. Therefore, the Seebeck coefficient and power factor of these samples remain superior even at high carrier concentration. At 723 K, the maximum power factor of (GeTe)₁₃Bi₂Te₃ compound is 2.88×10 ^-3 W?m ^-1?K ^-2 and the maximum ZT of (GeTe)₁₃Bi₂Te₃ is 1.27, which is 16% higher than that of pristine GeTe.