An optical fiber Fabry-Perot (F-P) acoustic sensing experimental device based on spectral demodulation is designed. The device is mainly composed of a superluminescent light-emitting diode (SLED) light source, a high-speed spectrum module and a field programmable gate array (FPGA) based signal processing circuit. The air gap between the end face of the single-mode fiber and the sensitive diaphragm constitutes the F-P cavity, which converts the acoustic signal into the variation of the cavity length. The interference spectrum signal is collected at a high speed by FPGA, which demodulates the cavity length in real time. As a result, the high-sensitivity detection of acoustic signals is realized. The experimental teaching device involves many contents such as optical fiber sensing, optical interference, photoelectric detection, FPGA, and digital signal processing, and is suitable for professional teaching experiments of optoelectronic senior undergraduates.