A high precision fiber Bragg grating wavelength demodulation system based on spectrum segmentation is proposed and experimentally demonstrated. Fabry-Perot etalon is added into the traditional Fabry-Perot filter method to dynamically calibrate the read-out value of the filter wavelength, which can eliminate measurement errors caused by the temperature drift effect or the peristaltic effect of Fabry-Perot filter. Meanwhile the amplified spontaneous emission (ASE) spectral characteristics and etalon are used to segment the wavelength for demodulation, which can greatly reduce the effects of the nonlinear effect of Fabry-Perot filter to improve the demodulation accuracy of wavelength and enhance the stability of the demodulation system. The result shows that stability of the system is 0.97 pm, the resolution is 0.33 pm, and the linearity of temperature is 0.9999.