The invention provides a long-distance and wide-measurement-range rapid demodulation device and method. The device comprises a laser, a first optical fiber coupler, a first electro-optical modulator IM1, a second optical fiber coupler, a delay optical fiber, a third optical fiber coupler, an erbium-doped optical fiber amplifier EDFA, a pulse module, a second electro-optical modulator IM2, an optical isolator, a microwave source module, a first circulator R1, a second circulator R2, a fiber grating filter, a photoelectric detector, an acquisition card and a to-be-tested single-mode fiber. According to the scheme, rapid temperature measurement is achieved through a polarization separation detection technology, and temperature demodulation is achieved through artificial neural network. Meanwhile, the difference pulse is used for improving the spatial resolution by adopting the Brillouin optical time domain analysis technology, and two optical pulses with different pulse widths are also required to be differentiated, and the polarization separation detection technology is used for generating the two optical pulses with different widths at one time to replace the switching of the two pulses, so that the pulse switching time is saved during measurement, and the measurement speed is further improved.