The invention discloses a measurement method and a device of a difference between facial expressions. By two near-infrared probes arranged at ear frontal acupoints of left and right ears, signals reflected by the brain frontal regions corresponding to the ear frontal acupoints are extracted by a signal extraction circuit, the extracted signals are input by an X channel and a Y channel of an oscilloscope, and are displayed on the oscilloscope in a way of Lissajous figures superimposed into ball spots in an X-Y working mode, and a facial expression is identified by comparing the differences between areas comprised in corresponding ball spot movement trajectories before and after the facial expression changes. In the measurement method and device, only two near-infrared probes are utilized to measure the ear frontal acupoints corresponding to the brain frontal regions, and the ball spots superimposed by the Lissajous figures displayed by the extracted ear frontal acupoint signals on the oscilloscope are directly compared, accordingly, the accuracy is high, the structure is simple, the external filtering is not needed and the interference of noise is not considered, the method and device can be used for being tested in various environments, and can be widely used and popularized.