The invention relates to a preparation method of rare-earth luminescent nanometer particles based on pyridine dicarboxylic acid. The rare-earth luminescent nanometer particle comprises SiO2 coating luminescent rare-earth composition; the rare-earth composition is produced by ligand pyridine dicarboxylic acid combined with rare-earth ions; and SiO2 nanometer particles with active functional group on the surface are formed by the polymerization reaction of the rare-earth composition in the microemulsion and the silanization. The prepared rare-earth luminescent nanometer particle has high luminous intensity and good water solubility, and can be used for a variety of time-resolved fluorescence analysis and imaging. Compared with the homogeneous rare-earth nanometer particle preparation method, the preparation method has the advantages of low preparation cost and simple method, and can be widely applied.