Combining with fiber Bragg grating Fabry-Perot interferometer (FBG-FPI) with cylinder oscillator coupling technology, a highly sensitive sensor is designed for detecting acoustic signal in liquid dielectrics of electrical equipment. A fiber Bragg gratting (FBG) with reflectivity of 50% is cut in the middle to produce two identical half-length Bragg gratings, and a piece of 20-mm SMF-28 monomode fiber is spliced between the FBGs to produce the FBG-FPI. The parameters of the cylinder oscillator are determined for high sensitivity by finite element analysis method based on the theory of elasticity. A novel method of temperature compensation using a tunable distributed feedback (DFB) laser is presented to solve FBG-FPI static working point drift influenced by temperature change. The effect of temperature compensation is proved by raising and falling temperature experiment. A contrast system with FBG-FPI sensor and RC6500T transducer is designed and constructed. The experimental results show that FBG-FPI in liquid dielectrics has the same sensitivity as acceleration transducer for the 1.1 kHz acoustic signal.