Abstract: Taking cracking of cumene as the model reaction and using Hammett indicator method, high temperature ammonia adsorption method and ESRtechnique, we have studied primitively the correlation between activity, coking and acidity of 4 rare-earth exchanged Yzeolite cracking catalysts and other solid acids.From our results can be seen:1. More active sites of catalysts are favorable to coking, leading their faster deactivation.2. For cracking of cumene at 250℃ the active sites which make contribution to cracking activity seem to be.Sites whose range of strength is H₀≤5.6, according to Hammett indicator method;Sites whose range of desorption temperature is T>250℃, according to high temperature ammonia adsorption method.