The invention provides a dropper type gas flow measuring device and method based on a weighing principle. The dropper type gas flow measuring device comprises an electronic scale, an oil storage tank, a dropper, a dropper support, a gas inlet valve, a fine adjustment valve, a three-way tube and a computer, wherein the oil storage tank storing oil is arranged on the electronic scale, a lower-end dropper orifice of the dropper installed on the dropper support is located under the oil liquid level, an upper-end dropper orifice of the dropper is communicated with the gas inlet valve and the fine adjustment valve through the three-way tube, and the fine adjustment valve is communicated with a measured object. The electronic scale is connected with the computer, and weigh data and the time for the measuring process are recorded and stored through the computer. The dropper type gas flow measuring method comprises the steps that the gas inlet valve is turned on; the fine adjustment valve is adjusted to enable gas flow passing through the fine adjustment valve to meet the gas inlet requirements of the measured object; an initial weigh reading is recorded; the gas inlet valve is turned off; gas flow measurement continues, a plurality of continuous time points are recorded in real time, meanwhile weigh readings corresponding to the time points are recorded; when the computer judges that measurement is needed to stop, the gas inlet valve is turned on, and the measurement process is finished; outflow gas flow is calculated.