N-type Se&Lu-codoped Bi₂Te₃ nanopowders were prepared by hydrothermal method and sintered by spark plasma sintering technology to form dense samples. By further doping Se element into Lu-doped Bi₂Te₃ samples, the thickness of the nanosheets has the tendency to become thinner. The electrical conductivity of Lu_0.1Bi_1.9Te_3-xSe_x material is reduced with the increasing Se content due to the reduced carrier concentration, while the Seeback coefficient values are enhanced. The lattice thermal conductivity of the Lu_0.1Bi_1.9Te_3-xSe_x is greatly reduced due to the introduced point defects and atomic mass fluctuation. Finally, the Lu_0.1Bi_1.9Te_2.7Se_0.3 sample obtained a maximum ZT value of 0.85 at 420 K. This study provides a low-cost and simple low-temperature method to mass production of Se&Lu-codoped Bi₂Te₃ with high thermoelectric performance for practical applications.