Cancer has become the leading cause of death for its high incidence and mortality. Early diagnosis and treatment are essential for the inhibition of tumor growth. In this work, A biocompatible, nontoxic, near-infrared fluorescent tumor targeting nanoparticle KHLF(K5HoLi2F10) was prepared by a delicate method for the early diagnosis of tumor. The surface functionalization of the nanoparticle endows it with good water solubility and biocompatibility. Covalent binding to folic acid provides it with the ability to target HeLa cells. After modification, this nanoparticle can still maintain high fluorescence intensity and it can be detected in 2 cm thick pork tissue. We carried out biodistribution imaging, organs imaging and tumor targeting imaging experiments to characterize its imaging ability in vivo. The results show that this nanoparticle could accurately accumulate in HeLa tumor and generate significant fluorescence signal, which confirms the nanoparticle has great potential as a efficient biocompatible fluorescent contrast agent for tumor diagnosis. © 2021 Elsevier B.V.