Metal-organic frameworks (MOFs) are composed of metal ions and organic linkers through coordination chemistry. Their molecular properties, functional diversity and adjustable structure and composition are different from the traditional inorganic material. Different from other nanomaterials, as a new type of porous crystal materials, nano-MOFs(NMOFs) not only maintains the structural diversity and properties of MOFs both in physics and chemistry, but also shows particle sizes ranging from tens to hundreds of nanometers. These advantages make NMOFs exhibit excellent performance in gas adsorption and separation, catalysis, magnetism, sensing, biomedical application, etc. Because NMOFs have the characteristics of large specific surface area, high porosity, adjustable internal pore size and functionalized surface, they have attracted more and more attention as biological imaging agents. In this paper, we reviewed the literature of NMOFs and their composites for imaging in the past 15 years, and summarized the research progress of NMOFs as biological imaging agents, including single imaging technology and composite imaging technology, providing the basis for the subsequent researchers.