Optical fiber MEMS sensor is a new sensor combined with MEMS micromachining and micro-optics technology, which has the advantages of miniaturization, strong anti-electromagnetic interference, ease of integration, easy to form array, low cost and high reliability. According to the need of low-frequency acoustic field measurements, the acoustic measurement theory of optical fiber MEMS is researched. The theoretical model of Fabry-Perot (F-P) interference measurement acoustic is built. And low-frequency acoustic sensor samples of optical fiber MEMS are designed and manufactured. The test result shows that the performance of optical fiber MEMS can meet high sensitivity acoustic measurement requirement in the band of 4 ~5 000 Hz.