A gas path flow monitoring apparatus and method for an ion mobility spectrometer. The gas path flow monitoring apparatus comprises: an ion migration tube, a sensor group, and monitoring device. The ion migration tube has a drift gas inlet, a carrier gas inlet for a sample gas, and an exhaust outlet. The sensor group comprises a drift gas intake quantity sensor connected to the drift gas inlet, a carrier gas intake quantity sensor connected to the carrier gas inlet, and an exhaust quantity sensor connected to the exhaust outlet. The monitoring device is connected to the sensor group to monitor a drift gas intake quantity sensed by the drift gas intake quantity sensor, a carrier gas intake quantity sensed by the carrier gas intake quantity sensor, and an exhaust quantity sensed by the exhaust quantity sensor. By means of the gas quantity control of the ion mobility spectrometer, the actual gas path flow situation is reflected, and thus the flow control precision is improved.