Abstract: A ranking of new matrixes containing different weight of phosphorus was made by treating metakaolin with phosphoric acid,and then mixed these matrixes with REY and bindings to form FCC catalysts also containing different weights of P.After being characterized by FTIR and MAT,it was found that with increasing P content,the number of total acid sites and Bronsted acid sites on cat.Surface are decreasing,but the ratio of Lewis acid sites number to total acid site's is increasing;and there is no strong Bronsted acid on the samples' surface;tt was found also that the activity increases with the increase of samples' acid density and that the strong Lewis acid sites relate highly to the coke formation.