Sipping test device is used to identify the tightness of the irradiated fuel assembly during refuelling campaign. The gas is selected as the medium and the xenon-133 as the indicating nuclide. The device consists of the gas system, the γ-activity detection and measurement system, the power supply and signal system, the mechanical components and parts. The device has satisfactory functions, e.g. easy operation, indication in instrumentation, chart record and acoustic alarm, which can meet the operation demand of the nuclear reactor.