Abstract: In the present paper,mixing time was determined in bubble columns of inside diameter 200 mmand 400 mm with and without internal parts within the superficial gas velocity (Ug) of 0.006—0.250 m/s and the high diameter ratios of 0.8—7.0 in the case of different structural parameters, such as aspect ratio (H/D) and sparger types including single-pipe,four-pipe, perforated plate and porous plate, using tap-water and acetate acid aqueous solution as liquid phase and air as gas phase.It was concluded that in the case of low mixing time it dropped strongly with increasing the superficial gas velocity whileit hardly changed with Ug and increasesignificantly with increasing aspect ratio H/D of bubble column in the case of large mixing time. The mixing time in the acetate acid system was 2—3 times larger than that in the tap water system at the "jumping point",viz. superficial gas velocity of 0.1 m/s due to foaming. Without foaming, the mixing of liquids was not influenced vidently by ion strength and surface tension.The mixing time prolonged by introducing a draft tube. Mixing time was prolonged and the effect of Ug extended in a larger range and showed extremum points when cross heat exchange tube was introduced.