Fly ash-derived zeolites were synthesized by hydrothermal treatment of fly ash in NaOH solution, The effects of synthesis conditions including NaOH concentration and reaction time on the mineralogical structure of the zeolites were investigated and the effects of these fly ash-derived zeolites on the pyrolysis behaviors of low density polyethylene and polypropylene were delineated in terms of the recovery and simulated boiling point distribution of the liquid pyrolysis products. It appeared that the fly ash-derived zeolites were not so much effective for LDPE pyrolysis, but slightly effsctive for PP pyrolysis.