A nuclear molecular imaging contrast agent. The nuclear imaging contrast agent comprises a polymer according to the structure of wherein, P is and 1 is not less than 1; D is a C3-30 dendritic moiety having a plurality of oxygen residue; Z is a C3-20 moiety having a plurality of functional groups, wherein the functional groups comprise carbonyl, carboxyl, amine, ester, amide, or chelate group; L is a radioisotope or analyte-specific moiety ; m is not less than two ; and at least one X is an analyte-specific moiety; the other X can be hydrogen atom.