Fiber Bragg grating (FBG) has been widely used in monitoring structural health, mechanical operation, aerospace field, and other physical parameters due to its advantages of being lightweight, tiny scale, immune to electromagnetic interference and multiplexing capability.Tunable scanning laser (TSL) was introduced to fabricate an accurate FBG wavelength demodulating system in the near infrared range (NIR) to achieve high-speed, wide-range, and high-precision demodulation. One fiber Fabry–Perot etalon (FFPE) was used as a wavelength marker to extract wavelength. The wavelength scanning range was subdivided to implement piecewise linear demodulation, which solves the nonlinear problem brought about by tunable scanning laser. Another fiber Fabry–Perot etalon was introduced to realize high-accuracy calibration of the demodulation. A polynomial least square curve fitting algorithm was proposed to further enhance demodulation accuracy and stability. This work has been utilizing a near-infrared wavelength scanning laser with a wavelength range of 1525-1565 nm. It showed a very promising result whereby the accuracy of the demodulating system exceeds ±0.5 pm, which achieves high accuracy, simplification and miniaturization.