Abstract: Dealumination extent affects the catalytic activity and selectivity of zeolite. A series of NH4NaY zeolites were prepared. The effect of calcination temperature, calcination time, Na+ concentration and air humidity on the dealumination extent was analyzed by 27Al small angle MAS NMR experiment. As it turned out, when the NH4NaY sample was calcined in air, the calcination temperature affects the formation of the total extra-framework aluminum and extra-framework aluminum species. When the calcination temperature is high, Na+ content influences the amount and composition of extra-framework aluminum species. Na+ content affects only the amount of extra-framework aluminum when calcination temperature is low. In addition, the calcination time affects dealumination degree, depending on calcination temperature and Na+ content. The calcination time has a complex influence on dealumination degree. The calcination time has no effect on the dealumination degree when calcination temperature is low, while at high calcination temperature, the influence degree reduces as Na+ content increases. The degree of dealumination is also affected by air humidity. The higher the humidity, the more aluminium is removed from the molecular sieve framework.