Abstract: The operation parameters of the centrifugal air classifier were tested and optimized for FCC catalyst fine powder from a calciner exit gas. The optimized operation conditions are: total air rate is of 2620 m3/h, wheel speed of classifier of 930 r/min，primary air and secondary air are 92% and 8% of the total air flow, respectively. Under the optimal operation conditions, the fine powder was clearly classified to coarse and fine parts. The content of particle less than 20 μm in the coarse part is decreased to 15.2% from its original 64% in the powder from calciner exhaust gas. But it reaches to 92.5% in the fine part. The Newton classification efficiency is 78.2% and the calculated cut size is 26.5 μm.