With pure metal Bi, Te, Se, SbI3 and Gd powder as raw materials, n-type Bi2Te2.7Se0.3 doped with Gd were fabricated by a high pressure sintering method and then annealed for 36 h in a vacuum atmosphere at 573, 603 and 633 K for 36 h. The samples were characterized by X-ray diffraction and scanning electron microscope. The electric conductivity, Seebeck coefficient, and thermal conductivity were measured from 298 to 473 K. The formulas about the relationships among energy gap, volume and pressure have been established. The results show that the samples are consisted of nanocrystal grains before and after annealing. For the HPS sample with Gd doping, the cell size is bigger, and the band gap width is narrower. The electrical conductivity and Seebeck coefficient increase but thermal conductivity decrease after annealing. The maximum ZT value is 0.74 at 423 K, after the sample is annealed at 633 K for 36 h