Abstract: Catalytic cracking experiments of straight-run diesel were conducted in a fixed fluidized bed reactor to study the effect of operation parameters and catalysts containing three different zeolites on product slates.The results showed that the straight-run middle distillate rich in naphthenic hydrocarbons and monocyclic aromatics has a higher yield of light aromatics.The higher conversion rate and gasoline and light aromatics yields are obtained using Y type zeolite catalyst and the light aromatics yield is up to 13.32%.As the reaction temperature increases from 510 ℃ to 610 ℃，the conversion is increased by 12.95 percentage points and the yield of light aromatics is increased by 7.16 percentage points.The ratio of catalyst/oil has little effect on the yield of light aromatics，but the yield of gasoline decreases when the ratio is too high.The cracking products have 26.4 percentage points naphthene less than that of the SR diesel feed，indicating more than 80.94% naphthene hydrocarbons to participate in the reaction.The more ring number in the naphthene，the higher the proportion of the naphthene involved in the reaction.

Key words: straight-run distillate, catalytic cracking, light aromatics, zeolite