Abstract: The effect of temperature on the aromatic balance in FCC was simulated using hydrotreated diesel as a feed in a laboratory fixed-fluidized bed (FFB) unit. Test results show that the total amount of aromatics in the product increases by about 9%~12%, compared with the hydrotreated diesel feed, at any reaction temperature. The total amount of monocylic aromatics in the product has little changes in the test temperature range, but is lower than that of the feed. With increasing the temperature, the proportion of the monocyclic aromatics in gasoline is getting higher, but is becoming increasingly lower in diesel. The amount of di-aromatics decreases as the temperature increases, however is significantly higher than that of the feedstock. The amount of tricyclic aromatics and coke increases with temperature. A conclusion can be drawn that the main reason for the total aromatic unbalance is the aromatics generated from naphthene through dehydrogenation.