Abstract: During the operation of a molten salt reactor, the continuous removal of gaseous fission product ¹³⁵Xe from the circulating fuel has to be provided. As one of the key devices in the off-gas removal system, the bubble generator is for generating tiny bubbles with average bubble diameter around 0.5 mm. Firstly, certain amount of helium bubbles are injected to the fuel, the bubbles absorb ¹³⁵Xe, and then these bubbles containing ¹³⁵Xe are stripped out of the fuel for removing ¹³⁵Xe in the liquid fuel. In the present study, a new bubble generator was designed for TMSR referenced to the design of ORNL. Meanwhile, a water test loop was fabricated for visualization observation on the performance of the bubble generator. The movement and breakup of the bubbles were recorded by a high speed camera. The effect of gas and liquid flow rates on generated bubble diameter was also analyzed. The results show that under experimental conditions, with the increase of liquid flow rate, the bubble size decreases with the increase of liquid flow rate when the gas flow rate remains unchanged; the bubble size increases with the gas flow rate when the liquid flow rate is constant.