The invention relates to a graphite-phase carbon nitride/rare earth sodium molybdate salt heterojunction photocatalyst, a method for preparing the same and application of the graphite-phase carbon nitride/rare earth sodium molybdate salt heterojunction photocatalyst. The method includes steps of S1, dissolving sodium molybdate and rare earth salt in water to obtain mixed solution; S2, adding ethylene glycol into the mixed solution in stirring states; S3, adding non-porous graphite-phase carbon nitride into the mixed solution and the ethylene glycol and carrying ultrasonic dispersion to obtainhomogenous solution; S4, placing the homogenous solution in a reaction kettle at the temperature of 100-200 DEG C, carrying out reaction for 2-10 h, and cooling, washing and drying reaction products to obtain the graphite-phase carbon nitride/rare earth sodium molybdate salt heterojunction photocatalyst. The molar concentration of the sodium molybdate in the mixed solution is 0.01-0.5 mol/L, and the molar concentration of the rare earth salt in the mixed solution is 0.005-0.25 mol/L. A usage ratio of the ethylene glycol to the sodium molybdate is 200-10000 mL/mol. The graphite-phase carbon nitride/rare earth sodium molybdate salt heterojunction photocatalyst, the method and the application have the advantages that the graphite-phase carbon nitride/rare earth sodium molybdate salt heterojunction photocatalyst which is a visible light response antibiotics degradation photocatalyst and is high in activity and stability can be successfully prepared by the aid of the method, the method includes simple processes, and the graphite-phase carbon nitride/rare earth sodium molybdate salt heterojunction photocatalyst and the method can be widely popularized and applied.