For the current of the Gallium Arsenide optical fiber temperature sensing technology not described in detail and have low demodulation precision, based on the relationship of absorption spectrum of the Gallium Arsenide fiber optic temperature sensor varying with temperature, a new data processing flow is proposed, and a temperature demodulation method is researched based on the spectral analysis of Arsenide fiber absorption optical fiber temperature sensing technology. This article used standard temperature measurement system to verify the reasonableness of the demodulation method and data processing procedure. The results show that in the range of 25℃~70℃, the measurement accuracy is less than ±0.1℃, and in the range of 70℃~250℃, the measurement accuracy is less than ±0.7℃.