The MOEMS acoustic sensor is a new technology which combines acoustic sensor technology with MEMS technology and micro-optics technology.The sensors have high sensitivity and may be used in heavy magnetic,electric fields.In case of warning and detecting antisubmarine aircraft by submarine,the acoustic sensor array which has high sensitivity,good response at low frequency and miniaturized is needed.To meet the requirement,a low frequency MOEMS acoustic sensor based on light intensity modulation is designed.Static performances of membranes with several sizes are simulated with Finite Element modeling,and the parameters of membrane are given out.The characteristic of reflected light intensity is simulated and experimented.The low frequency MOEMS acoustic sensor is made of membrane,the wavelength of the LED is 850 nm.Experiment shows that the sensor has good response in low frequency and its sensitivity is 200 mV/Pa,which reach the aim of the design.