<p>The rapid development of nuclear energy necessitates reliable radioactive waste forms to ensure sustainable nuclear industry growth. Conventional cement or glass matrices face critical limitations, including insufficient chemical durability and low radionuclide loading. Inorganic ionic co-crosslinking polymerization is a novel method to produce compact inorganic materials, which can achieve plastic preparation of inorganic blocks at the molecular scale and has not yet been used to immobilize radionuclides. This study utilizes calcium carbonate phosphate compounds (referred to as CaCP) with molecular homogeneity, synthesized through a controlled crosslinking polymerization method utilizing inorganic ion oligomers to immobilize cationic radionuclides for the first time, such as representative strontium, europium, and uranium. CaCP is compared with calcite and hydroxyapatite waste forms synthesized through the same method. The results demonstrate that CaCP exhibits superior chemical stability, mechanical strength, and cost-effectiveness. The normalized leaching rates for strontium, europium, and uranium are recorded at 1.33×10⁻⁶, 4.89×10⁻¹⁰, and 3.05×10⁻⁹ g m⁻² d⁻¹, respectively. Structural characterization elucidates the immobilization mechanism and demonstrates the CaCP’s high immobilization efficiency and enhanced properties, while theoretical calculations further support the structural insights. This work highlights the potential of CaCP as a promising candidate for advanced radioactive waste management.</p>