The invention relates to an optical fiber liquid level measurement device and an optical fiber liquid level measurement method and belongs to the technical field of optics. The invention aims at solving the problems that an existing optical liquid level sensor is complex in manufacturing process, low in measurement accuracy, small in measurement range and unstable in device structure. The optical fiber liquid level measurement device comprises a laser, an optical fiber coupler, a polarization controller, an electrooptical modulator, an erbium-doped optical fiber amplifier, a microwave source, an arbitrary-function generator, a circulator, an optical fiber Bragg grating, an optical isolator, a sensing optical fiber, a self-heating type optical fiber, a photoelectric detector, a data acquisition card and a power meter. The optical fiber liquid level measurement method comprises the following steps: combining a Brillouin optical-time domain analysis technology with the self-heating type optical fiber, wherein the self-heating type optical fiber converts optical energy into heat energy and is pasted with the sensing optical fiber together to realize thermal transmission; and immersing a sensing part into liquid, judging the position where the liquid level is located by virtue of a temperature abrupt change point, thereby realizing centimeter magnitude resolution, meanwhile, measurement range is tens of centimeters, so that high-resolution and high-accuracy liquid level measurement is realized.