The invention discloses an all-fiber Fourier transform Raman spectrometer, which includes transmission fibers, a laser, a fiber Raman probe, an all-fiber dual-beam interference system, and a photomultiplier. The laser, the fiber Raman probe, the all-fiber dual-beam interference system and the photomultiplier are associated with each other by means of the transmission fibers. The laser is irradiated on a sample through the fiber Raman probe and forms Raman diffusion light. The Raman diffusion light is collected by the fiber Raman probe and enters the all-fiber dual-beam interference system, and therefore two paths of interference light are formed. One light path of the two paths of interference light is modulated by a phase modulator in the all-fiber dual-beam interference system, and the modulated interference light is output to the photomultiplier and converted into an electric signal. Fourier transform of Raman spectrum is achieved and then spectrum demodulation is realized by means of the all-fiber dual-beam interference system, and dual-beam light path difference modulation is performed by an all-fiber phase modulator. The all-fiber Fourier transform Raman spectrometer, becoming miniature, is high in resolution, high in signal to noise ratio, wide in spectrum scope and low in cost.