The application mode of execution discloses a while-drilling gas cut simulated experimental device and an experimental method. The device comprises a gas-liquid conveying mechanism, a shaft simulated experimental mechanism and a data processing mechanism. The gas-liquid conveying mechanism comprises a gas-liquid mixer, a gas branch road and a mud branch road, wherein the gas branch road and the mud branch road are connected with the gas-liquid mixer, the gas branch road comprises a gas compressor and a gas storage tank which are mutually connected in sequence, and the gas storage tank is connected with the gas-liquid mixer; the mud branch road comprises a mud tank, a heater and a plunger pump which are mutually connected in sequence, and the plunger pump is connected with the gas-liquid mixer; the shaft simulated experimental mechanism comprises a Doppler ultrasonic theory experimental section and an underground overflow simulated test section; and the data processing mechanism comprises a front-end amplifier, a modulus collector and a computer which are connected in sequence, and the front-end amplifier is connected with the shaft simulated experimental mechanism. The technical scheme of the while-drilling gas cut simulated experimental device and the experimental method can provide data support for detecting gas cut precisely and timely.