In this paper, we propose a fiber-optic multifrequency Fabry-Perot (FP) acoustic vibration sensor based on a graphene oxide (GO) microcavity. The sensor uses a single-mode fiber end face and GO film to form a micron-scale FP interference microcavity structure. The GO film is prepared by liquid-phase method and used as a sensitive material to detect the external acoustic vibration signals. Through controlling and optimizing the length of the FP microcavity, the interference spectrum with the largest extinction ratio can be obtained, and single-, dual-, and triple-frequency acoustic vibration signals of different frequencies are applied to the sensor to test its response capability to multifrequency signals. The experimental results show that the sensor has a high signal-to-noise ratio (SNR); the SNR for single-frequency vibration signal sensing can reach up to 61.8 dB, and the frequency response range is wide, approximately 500 Hz?20 kHz; the highest SNR for dual- and triple-frequency acoustic vibration signal sensing can reach 56.8 dB and 54.4 dB, respectively.