Abstract: In order to explore a rapid synthesis method for Gd₂Zr₂O₇ pyrochlore immobilizing actinide elements from radioactive wastes, Gd_1.6Nd_0.4Zr₂O₇ pyrochlore was synthesized via solid state reactions for 15 min under high pressure (3-4 GPa) and high temperature (1 573-1 673 K). The products were characterized by powder X-ray diffraction and scanning electron microscopy. The results indicate that among all the compositions, Gd_1.6Nd_0.4Zr₂O₇ solid solution with a cubic pyrochlore structure is synthesized within only 15 min. This period is approximate 200 times faster than other common preparation methods with synthesis time of not less than 48 h. The phase transition pressure and temperature of the samples are expanded under high pressure and temperature conditions. The stability of the pyrochlore phase is found to increase. The lattice parameters of Gd_1.6Nd_0.4Zr₂O₇ solid solutions gradually increase with the neodymium content and the synthesis temperature, and decrease with the increase of the synthesis pressure.