Abstract: The liquid lithium as core coolant of lithium cooled fast reactor continues to react with neutron emitted from the core to produce helium, which will not only interfere core cooling, but also reduce the efficiency of thermoelectric converter and electromagnetic pump. Therefore, the helium produced needs to be removed. In order to study the gas-liquid separation technology for the helium removal of the core coolant of the lithium cooled fast reactor, the passive gas separator and accumulator device (GSA) for SP-100 reactor of the USA is used for reference. According to its structure and principle, GSA can realize gas-liquid separation and gas storage mainly by the centrifugal force generated by its front vane and main vane, as well as the surface tension generated by its filter and gas storage screen. While Weber number is the ratio of inertial force and surface tension, which can represent both centrifugal force and surface tension. Therefore, Weber number is introduced here as the criterion number, helium and lithium are replaced by air and water, and then air-water separation experiment scheme for theoretical verification is firstly designed. During the experiment, the gas volume portion at the inlet of the experimental prototype will be kept at a low level (less than 1%), the Weber number of the experimental condition will be equal to the one of the actual condition and the inlet of the experimental prototype will contain bubbles with a diameter greater than 200 μm. Then, according to the experimental requirements the experimental prototype has been developed whose main material adopts transparent plexiglass facilitating the observation of its internal fluid conditions. Several structural parameters of the experimental prototype are consistent with the corresponding structural parameters of the GSA. However, since the remaining structural parameters are not clear, the detailed structural design is carried out in the development of the experimental prototype, such as the front vane, the main vane, the filter, the gas storage screen, etc., then the appropriate structural parameters are selected through CFD. Finally, to demonstrate repeatability, three experiments are carried out on the experimental prototype. Every time the experimental conditions include the air-water flow with a gas volume portion of less than 1%, the water velocity close to 0.88 m/s and the bubble size range of 0-900 μm. The experimental results show that the experimental prototype can effectively gather and store the bubbles with the size greater than 200 μm, and make its degassing efficiency exceed 90%, conform to the working principle of the GSA.