With a view to obtaining better gasification performance, pyrolytic gasification of polyethylene (HDPE) by partial combustion was carried out in a porous alumina fluidized bed with a conical gas distributor and the effects of operating conditions on gasification products were studied experimentally. To clarify the gasification process, the alumina particles were taken out of the column during the run and substances forming on the alumina particles were imaged by SEM and analyzed by using a mass spectrometer. The product gas is of higher heat value than that in a fluidized bed with a perforated plate gas distributor because the product gas includs many C3-5 Of hydrocarbons with a conical gas distributer under the optimum conditions of air ratio of 0.2 to 0.3, and bed height/column diameter ratio of 1.0 to 1.5. The amount of carbonaceous substances retained in the alumina particles with a conical gas distributor is 20 to 30% of those with a perforated plate gas distributor, while mass spectra show that carbonaceous substances with a conical gas distributor are 300 to 1,000 of molecular weight, and they are heavier than those with a perforated plate gas distributor.