A hot downer reactor of 4.5 m in height and 13 mm in inner diameter was built to examine its performance in the deep catalytic cracking (DCC) process. The experimental results show that the downer reactor can significantly improve the selectivity of desired products in comparison with the commercial riser adopting the same feed and catalyst: the yields of propylene and gasoline increase by 3.71 and 7.30 wt %, respectively, while the yields of dry gas and coke reduce by 6.77 and 1.98 wt %, respectively. The "close to plug flow" pattern of the gas and solids in the downer makes it a desirable reactor for the DCC process.