The invention relates to an optical fiber near-infrared spectrometer in the technical field of medical devices. The optical fiber near-infrared spectrometer uses multi-tail optical fiber collimator as light source optical fiber, uses a number lock technology as a technical scheme for weak signal extraction, uses a laser diode with a PD as a light source for sinusoidal modulation, uses an avalanche photodiode (APD) or photomultiplier tube (PMT) as a detector, and uses thick core-diameter plastic optical fiber, liquid-core optical fiber, silica optical fiber, a silica optical fiber bundle or glass optical fiber bundle as detection optical fiber. The invention has the advantages that the instrument can conduct nondestructive real-time hemodynamic parameter detection to biological tissues sheltered by hairs, the noise level of the instrument is low, the time resolution is high, the stability is high, the price is cheap, the hardware circuit design is greatly simplified and the portability of the instrument is realized.