The utility model relates to an oil-water-gas three-phase flow metering device, which makes a gas-liquid separating jug, a gas-liquid controlling jug, a fluid flow meter, an oil-gas-water compositional instruction, a gas metering instrument and a gas-liquid dashpot connected through a flange and a pipe line to form an oil-water-gas phase-splitting gage ductwork. The upper portion of the gas-liquid separating jug is connected with a gas-liquid admitting port, the upper portion and lower portion of the gas-liquid separating jug are separately connected with the upper portion and lower portion of the gas-liquid controlling jug through a gas discharging pipe and a liquid discharging pipe. The gas-liquid controlling jug is arranged with a float adjusting valve inside, a gas outlet pipe on the upper portion, and a liquid outlet pipe on the lower portion, wherein, the gas discharging pipe and the liquid discharging pipe are connected with the gas-liquid outlet pipe at the gas-liquid collecting pipe. The inner and outer portion of the whole device have no auxiliary electric control system, thereby the utility model has small volume, light weight, simple structure, steady and reliable extended service and small pressure loss. The utility model is suitable for the gas-liquid automatic phase-splitting on-line measuring of any flow pattern, in particular to measuring the multi-phase flow which has intermittent liquid and bigger gas-liquid change. The measuring accuracy can amount to +-0.5-2%, the phase-splitting flow measuring is steady, the measuring accuracy is not influenced by the flow type of gas and liquid and the liquid condition, thereby the dielectric viscosity range is wide (thin oil, heavy oil and the like).