Abstract: The coal fly ash sample was used to synthesize the zeolite adsorbent, and then the effect of lanthanum modification on phosphorus adsorption of the synthetic zeolite and its mechanism were investigated to help to reduce phosphorus pollution in water. The physicochemical properties of the synthetic zeolite before and after La-modification were systematically characterized by using various analytical techniques. Specifically, the differences of major components, mineral composition and structures before and after modification were explored. Furthermore, the phosphorus removal mechanism was preliminarily discussed from the perspectives of isothermal adsorption experiments, adsorption kinetics experiments and adsorption thermodynamics calculations. The results indicated that the phosphorus removal rate of the La-modified synthetic zeolite reached 94.2% in the simulated wastewater system, which was nearly 65 percentage higher than that without modification. Moreover, the lanthanum ions were physically loaded on the surface of the synthetic zeolite after modification, which enhanced the phosphorus adsorption. The phosphorus adsorption process conforms to the Langmuir adsorption isotherm model and the Elovich equation, and the adsorption happens spontaneously. The study has provided a theoretical and practical basis for promoting the utilization of coal fly ash and eliminating the phosphorus pollutants in water.