The effect of pressure and temperature on the axial dispersion of gas was examined in a fluidized bed of 10 cm I.D. x 100 cm, height. The employed particle was zinc titanate catalyst and particle size was 150,um. The stimulus-response method was employed in order to determine the axial dispersion coefficient of gas in a bubbling fluidized bed. The hydrogen was used as the trace gas. The experimental results showed that the increase of pressure and temperature did not significantly change the axial dispersion coefficient in spite of significant increase of minimum fluidization velocity.