Abstract: The coagulation of the small crystal beta zeolite colloidal system in filtering system with the present of coagulating material NS and the mechanics of coagulation were studied. The colloidal structure of beta zeolite particles in the filtering system, by means of analyzing its existence state, is recovered. Meanwhile, the variation of Zeta electric potential, while the contra-ion extrudes Stern electric double layer, is analyzed, and the reason of coagulation is well explained. It is found that the small crystal beta zeolite can coagulate at the room temperature when the ratio of NS to beta zeolite (net weigh) is not less than 30%, which can increase the filtering efficiency of little crystal beta zeolite greatly. Relative crystallinity of beta zeolite coagulated by NS decreases a little, and the same time, the Na2O percentage content of beta zeolite drops with wide range. Experimental results provided by activity test on a light oil micro-test reaction apparatus state that beta zeolite coagulated by NS is also an excellent activity additive of FCC catalyst.