A₂B₂O₇ pyrochlore is considered as a candidate host matrix for high-level radioactive wastes due to its incorporation and physicochemical stability. Nd_1.8Th_0.2Zr₂O₇ and Nd₂Zr_1.8Th_0.2O₇ pyrochlore samples doped with 20% thorium (in molar) were successfully prepared by using spray-pyrolysis and high temperature sintering method. The structures of the synthesized immobilization were characterized, and the chemical durability tests were investigated by the MCC-1 method. Structural analyses show that samples Nd_1.8Th_0.2Zr₂O₇ and Nd₂Zr_1.8Th_0.2O₇ exhibit pure single pyrochlore structure. Rietveld refinement analyses show that the value of 48f oxygen site parameter of 20% thorium-doped Nd₂Zr₂O₇ pyrochlore increases, which suggests that the structure is transforming from ordered pyrochlore to disordered structure, as compared with Nd₂Zr₂O₇. The Nd_1.8Th_0.2Zr₂O₇ pyrochlore structure evolution results from the distortion of the AO₈ hexahedral structure, while the B-site substitution leads to partial deformation of the BO₆ octahedron. The leaching experiment results show that the normalized leaching rate of thorium is as low as 10^-5g·m^-2·d^-1 after 42 d. Thorium can be well incorporated at the A and B cation sites of the Nd₂Zr₂O₇ pyrochlore structure of which the immobilization exhibits the excellent physical and chemical properties.