Abstract: Based on the evaporating water tower of the circuit bottom ash sluicing system,the formation and movement of the single bubble emerging from an orifice with diameter of 5 mm in the middle of tray were investigated by visual experiments, with the water flow rate of 150, 200, 250 L/h, the steam flow rate of 5 kg/h, and nitrogen flow rate of 0.163 2 kg/h and 0.326 4 kg/h. The life time of bubbles was recorded by high speed camera and the characteristics of bubble deformation and movement were obtained by image processing software. The results show that the life time of bubble is divided into three parts on the basis of pictures:formation region, rising region and oscillation region. The bubble deformation and movement are obtained in each part. The equivalent radius of bubble increases rapidly in the first region because of the gas influx and grows more slowly in the latter two regions. The aspect ratio of bubble changes from large to small in the formation region, while it changes irregularly in the oscillation region. The vertical velocity of centroid of steam bubble increases at the beginning and then fluctuates. However, the vertical velocity of centroid of nitrogen bubble increases over time due to the lacking of mass transfer. The motion law of bubble in the oscillation region is hard to describe. The hollow phenomenon is found in both steam and mixture bubbles through the condensing process in the experiment. The effect of non-condensable gases to the transmission process is also discussed. With the increasing of the nitrogen flow rate, the time of formation and oscillation region decreases for the mixture gas bubble, leading to the deterioration of heat transfer in the tower. The result of this paper can be a theoretical guidance for evaporating hot water tower operation.