The invention discloses a rare-earth organic coordination polymer constructed by using m-phthalic acid and 2-pyridylformic acid as a mixed ligand, and a preparation method and application thereof. The preparation method is characterized by comprising the following steps: dissolving a rare-earth compound, m-phthalic acid, 2-pyridylformic acid and a nitrogen-containing compound in a solvent, wherein the mol ratio of rare-earth compound to m-phthalic acid is 1:(0.05-15), the mol ratio of rare-earth compound to 2-pyridylformic acid is 1:(0.05-15), the mol ratio of rare-earth compound to nitrogen-containing compound is 1:(0.05-15), and the mol ratio of rare-earth compound to solvent is 1:(500-10000); evenly mixing, regulating the pH value of the reaction system to 5-10 with acid or alkali, and adding the reaction system into a reaction kettle; and heating to 80-300 DEG C to react for 1-240 hours, gradually cooling to room temperature, filtering, washing with water, and drying to obtain the rare-earth organic coordination polymer constructed by using m-phthalic acid and 2-pyridylformic acid as a mixed ligand.