In order to obtain the strain information quickly and accurately, several methods for calculating the central wavelength variation of fiber Bragg grating(FBG) spectrum signals are studied and analyzed based on the fiber sensing application system of Fabry Perot(F-P) filter. According to the symmetrical characteristics of the power distribution waveform of the FBG reflection spectrum, an algorithm for optimizing the central wavelength value is proposed. Based on the two side data of the peak value of the two adjacent sampling spectral waveforms, the alternative value of the central wavelength is obtained by the optimization calculation according to the principle of the least square method. The experimental results show that the variation of the central wavelength of FBG spectrum calculated by this method is not more than one sampling point.