Multinuclear complexes as metallo-agents for clinical use have caught extensive attention. In this paper, using DOTA as both a functioning unit and a constructing junction, we build a series of DOTA-branched organic frameworks (DBOF) with multiple chelating holes by organizing DOTA layer by layer. These giant chelators are well characterized, which re-veals their nano-sized and soft structures. Further experiments demonstrate that they could efficiently hold abundant metal ions with much higher kinetic stabilities than the conventional small DOTA chelator. Their corresponding polynu-clear complexes containing Gd3+, Tb3+, or both show superior imaging properties, excellent feasibility for peripheral modi-fication, and unusual kinetic stability. This work can be easily extended to the fabrication of diverse homo-multinuclear complexes and core/shell hetero-multinuclear complexes with multifunctional properties. We expect that this new type of giant molecules and the ligand-branching strategy would open up a new avenue for the design and construction of next-generation polymetallic agents with high performance and stabilities for biomedical applications.