The invention discloses a composite wavelength reference-based fiber bragg grating sensing demodulation device and method. The composite wavelength reference-based fiber bragg grating sensing demodulation device includes a broadband light source (1), a tunable FP filter (2), an optical fiber primary beam splitter (3), an optical fiber circulator (4), an optical fiber grating sensing array (5), a first optical fiber secondary beam splitter (61), a second optical fiber secondary beam splitter (62), an optical fiber air chamber (7), an optical fiber FP etalon (8), a notching filter (9), a photoelectric detection array (10), a data acquisition card (11) and a processing unit (12); and the composite wavelength reference-based fiber bragg grating sensing demodulation device further comprises a sensing link and a wavelength reference link. Compared with the prior art, and according to the composite wavelength reference-based fiber bragg grating sensing demodulation device and method of the invention, equal-interval reference wavelengths can be provided by the optical fiber FP etalon, and therefore, advantages of high fineness of transmission peaks, easiness in peak finding and wide wavelength coverage range can be realized; absolute reference wavelengths provided by the optical fiber air chamber are not affected by environmental factors such as temperature, vibration and impact; and stable fiber bragg grating demodulation is realized.