The invention discloses a dynamic distributed Brillouin optical fiber sensing device and method, belongs to the optical field, and solves the problem of small strain measurement range in a dynamic sensing technology based on a Brillouin gain slope method. The dynamic distributed Brillouin optical fiber sensing device comprises a laser, a coupler, a to-be-measured polarization maintaining optical fiber, an erbium-doped fiber amplifier, an adjustable optical attenuator, a data acquisition module, a first polarization controller PC1, a second polarization controller PC2, a third polarization controller PC3, a fourth polarization controller PC4, a probe light intensity modulator IM1, a pump light intensity modulator IM2, an arbitrary waveform generator (AWG), a first circulator R1, a second circulator R2, a first signal amplifier Amp1 and a second signal amplifier Amp2. According to the invention, the intensity modulators can be driven by arbitrary waves, so that the frequency agility of probe light is realized, the fast frequency scan problem is solved, the distributed Brillouin dynamic sensing is achieved, and the strain of the to-be-measured polarization maintaining optical fiber is measured.