Abstract: Experiments of perhydrophenanthrene cracking over zeolite catalysts were conducted in a small fixed fluidized bed (FFB) unit. Effects of Y and ZSM-5 zeolite catalysts, temperature and catalyst/oil ratio on naphthenic ring opening reactions of perhydrophenanthrene were examined. The results show that products from naphthenic ring opening reactions of perhydrophenanthrene over zeolite catalysts are monocyclic or dicyclic cycloparaffin (cyclohexane, decalin), which is further converted into isoparaffin (2-methylpenptane, methyl hexane) by side chain breaking, or into monocyclic aromatics (benzene, C_1~4 alkyl benzene) by hydrogen transfer, or into dicyclic aromatics (tetrahydronaphthalene, naphthalene, alkyl naphthalene) by deep hydrogen transfer. Products from dehydrogenation condensation reactions of perhydrophenanthrene are polycyclic aromatics with more than 3 rings (phenanthrenes, pyrenes) and coke. Due to the influence of naphthenic diffusion and adsorption on catalysts, selectivity of the naphthenic ring opening reaction is higher over Y catalyst than that over ZSM-5catalyst. The relative ratio of naphthenic ring opening reactions to dehydrogenation condensation reactions, abbreviated as s (NRO) /s (DHC), is higher over Y catalyst than that over ZSM-5 catalyst. At the weight hourly space velocity of 10 h^-1, temperature of 475~550 ℃, catalyst/oil mass ratio of 3.0~9.0, reactions of bimolecular hydrogen transfer and dehydrogenation condensation became stronger, and selectivity of the products from naphthenic ring opening reactions decreases with the rising of temperature or catalyst/oil ratio over Y catalyst.