A nanoparticle for detecting or treating a tumor is provided. The nanoparticle includes a plurality of polymer backbones and at least one first detectable substance, of which each of the polymer backbones includes a hydrophobic region, a hydrophilic region and a chelating region, and the first detectable substance is bound to the chelating region of the polymer backbone. The hydrophobic regions of the polymer backbones form a core block, and the hydrophilic regions of the polymer backbones form a shell block surrounding the core block. A method for detecting or treating a tumor using the nanoparticle is also provided.
