Radiopharmaceuticals are playing an increasingly important role in the field of tumor diagnosis and treatment, with one of the core being the efficient and stable binding of radioactive isotopes with targeted molecules by chelating agents, and possessing high stability and good pharmacokinetic properties in vivo. This article systematically reviews the research progress of chelating agent labeling chemistry for classic and novel radioactive metal nuclides, with a focus on exploring the applicable chelating agents, labeling strategies, and in vivo application performance of key nuclides such as ⁶⁸Ga, ¹⁷⁷Lu, ⁹⁰Y, and ²²⁵Ac. By analyzing the thermodynamic stability, labeling conditions (pH, temperature, time), and in vivo kinetic inertness of radioactive nuclide chelating agent complexes, the influence of chelating agent structure on the targeting, stability, and efficacy of radiopharmaceuticals are revealed, providing theoretical and technical references for the development and clinical translation of radiopharmaceuticals.