In this paper, GdB6and CeB6 were used as raw materials,and hexaborides GdxCe1-xB6(x=0.0-1.0) bulk materials were successfully prepared by the spark plasma sintering (SPS). The effects of Gd doping on the phase composition, the mechanical properties, the resistivity and the thermionic emission properties of CeB6 base material were studied systematically. The research results show that high density GdxCe1-xB6 single-phase block material can be obtained by sintering at a temperature of 1550 oC, pressure of 50 MPa and holding time 5 min And the Vickers hardness of sintered samples can reach 24.02 Gpa.The thermionic emission properties results show that the right amount of Gd doped can significantly improve the electron emission properties of bulk materials, Gd0.1Ce0.9B6 composition block has the best thermal emission properties, of which the emission current density is 101.57A/cm2, the zero field current density is 21.94A/cm2 under an applied voltage condition of 4kV at 1600 oC, and is better than GdB6 and CeB6 block sample under the same conditions.