The invention discloses a modular distributed optical fiber sensing device which comprises a machine case, a modulation module, a photoelectric module, a signal collecting and processing module and a controller module. The modulation module, the photoelectric module, the signal collecting and processing module and the controller module are all matched with the type of a slot of the machine case, an embedded controller is adopted in the controller module, the modulation module generates electric pulses to drive a modulator in the photoelectric module to generate optical pulses, the optical pulses are output out of an optical interface of the photoelectric module, meanwhile, optical signals returned by measured optical fibers are received and are converted into electric signals by a photoelectric detector, the signal collecting and processing module collects and processes the electric signals transmitted by the photoelectric module, and a measuring result is transmitted to the controller module to be stored and displayed. The integrated, standardized and modularized production of the distributed optical fiber sensing device can be pushed, and therefore the flexibility and universality of the device are improved, and the cost of the sensing device is greatly lowered.