The effect of temperature profiles in the primary and secondary pyrolysis zones on thermal reactions of tar in the secondary pyrolysis was investigated in three kinds of flash pyrolyzers, an entrained-flow reactor, a fluidized-bed and a curie-point pyrolyzer, with Morwell brown coal and Wandoan high-volatile bituminous coal. The yield of mono-and diaromatic products was adopted as a measure of the vapor-phase reactivity of primary tar. The BTX and naphthalene yields for Wandoan coal was hardly affected by the primary pyrolysis temperature above 600℃, but that for Morwell coal was much influenced above 700℃.