Abstract: The factors affecting FCC naphtha olefin upgrading, such as the preheating temperature, regenerated catalyst temperature, mix temperature and catalyst to oil ratio in the mix zone were investigated in a continuous pilot riser-type FCC unit. The results showed that low regenerated catalyst temperature, low mix temperature and low catalyst to oil ratio can reduce the yield of coke and fuel gas, but impair the FCC naphtha upgrading effectiveness. The temperature of catalyst regenerated is the main factor that determines the yield of coke and dry gas, while the effectiveness of the FCC naphtha upgrading is mainly dependent on the ratio of catalyst to oil. The decrease of regenerated catalyst temperature, catalyst to oil ratio and mix temperature can reduce the conversion of olefins and the content of aromatics and i-paraffins; while the increase of the preheating temperature give the reverse effect. Therefore, the optimal conditions in the mix zone were high preheating temperature and low regenerated catalyst temperature with a proper reaction temperature and a proper ratio of catalyst to oil.