Single phase Gd 2−x Nd x Zr 2−y Ce y O 7 (0≤x, y≤2) ceramics were synthesized by a simple solid-state reaction method. The neodymium and cerium simultaneous substitution influence on the structure modifications were first investigated systematically. X-ray diffraction has been utilized to confirm adoption of pyrochlore or fluorite structure. XRD results show that structure modifications induced by simultaneous substitution are strongly dependent on the solubility of both Nd and Ce. It was found that the ordered pyrochlore structure was maintained for samples with 1.6≤x≤2, 0≤y≤0.4, from Gd 0.4 Nd 1.6 Zr 2 O 7 to Nd 2 Zr 1.6 Ce 0.4 O 7 . Whereas, the ordered pyrochlore structure was lost for samples with 0≤x≤2, 0.8≤y≤2, from Gd 2 Zr 1.2 Ce 0.8 O 7 to Nd 2 Ce 2 O 7 , and the structure transformed to fluorite. Furthermore, at the Gd 3+ and Zr 4+ positions, the whole of Gd 3+ and Zr 4+ could be replaced by Nd 3+ and Ce 4+ , respectively, with its end member Nd 2 Ce 2 O 7 was fluorite structure. The studies established the existence of a continuous range of Gd 2−x Nd x Zr 2−y Ce y O 7 (0≤x, y≤2) ceramics with a single phase structure.