In order to optimize the application of L zeolite in petroleum catalytic cracking, L zeolite was modified by different ion exchange methods. The effects of different ion exchange methods on reducing the potassium content of L zeolite and the changes of L zeolic acid properties after modification were investigated. The results showed that the combination of ion exchange and water vapor treatment was more effective in reducing the potassium content of L zeolite, and the potassium oxide content of L zeolite samples after tertiary ion exchange and tertiary water vapor treatment could be reduced to 0.82%. The results of NH3–TPD heating and desorption experiments showed that the strength of the acid center on the modified L zeolite surface increased, the acid strength distribution became wider, and the total acid content decreased. From the infrared pyridine adsorption spectra, it can be seen that B acid center and L acid center appeared on the surface of L zeolite after modification.