In the paper, the optical fiber Fabry-Perot (FP) interference microphone with dual wavelength demodulation is demonstrated. By using the normalization algorithm and differential cross multiplication (DCM) algorithm, the acoustic signal is accurately restored. In the normalization algorithm, through ellipse fitting, the optical signal with two-way wavelength is normalized, which can reduce the influence of the output fluctuation of laser on the output of optical fiber FP interference microphone. In the DCM algorithm, through signal processing and filtering, the accurate output of acoustic signal is realized, and the influence of temperature and other environmental factors on the output of optical fiber FP interference microphone is reduced. In the experiment, the characteristic of optical fiber FP interference microphone based on dual wavelength demodulation is tested by contrast method. The acoustic signal with sensitivity of 210 mV/Pa and frequency response of 100Hz-3150Hz is realized, which can be well applied in the field of speech recognition, noise measurement, and airborne acoustic detection.