Compared with traditional capacitive or piezoelectric acoustic sensors, fiber optic acoustic sensors have unique advantages, such as passivity, high temperature resistance, corrosion resistance, light weight, wide frequency response, and immunity to electromagnetic interference. Optical fiber acoustic sensing technology can solve the measurement problems that traditional electronic acoustic sensing technology is not competent for. Acoustic sensors based on Extrinsic Fabry-Perot Interferometer (EFPI) are widely reported in practical applications owing to their simple principle, rapid-response, convenient manufacturing methods and good mechanical property. EFPI fiber acoustic sensors are usually composed of fiber end faces and acoustic sensing thin films, and their acoustic sensing characteristics are mainly determined by the thin films. A cantilever beam is a simple micro-mechanical sensing element that can detect small displacements or forces, typically manifested as a fixed protruding beam structure. Due to the advantages of simple structure, unlabeled detection, and high sensitivity, micro-cantilever beam sensors based on Micro-Electro Mechanical System (MEMS) technology have received a lot of attention in fields such as physics, chemistry, medicine, environment, materials, etc. Manufacturing micro-cantilever beam on the end face of fiber to form EFPI sensors, this structure can combine the common advantages of micro-cantilever beam and fiber sensing. Compared with traditional mechanical cantilever beam systems, fiber optic cantilever beam sensors have the advantages of simple structure, compact size, and high optical stability. Femtosecond laser, as a flexible, efficient, and non-contact machining tool, has important applications in the field of micro and nano structure manufacturing. Through laser irradiation, energy can be injected into the target material in a short period of time and concentrated near the focal point. Compared with other areas not irradiated by the laser, the target area is easy to achieve changes in surface properties. The use of femtosecond laser processing for micro-cantilever beams has manufacturing advantages of high precision, high efficiency, and simple operation. In order to obtain high acoustic sensing sensitivity,the acoustic sensing characteristics of femtosecond laser processing micro-cantilever based on thin-film is studied theoretically and experimentally in this paper. In previous work, a silicone rubber film fixed at the end of a stainless steel sleeve was fabricated with spin coating and dipping method, and then a micro-cantilever beam was engraved on the silicone rubber film by using femtosecond laser. Finally, assemble the stainless steel sleeve that has fixed the film and the ceramic ferrule connected to the fiber, and fix it with epoxy resin to complete the assembly of the micro-cantilever beam silicone rubber film. The fabricated micro-cantilever beam structure has a length and width both of 500 μm and a thickness of 6 μm. The contrast of the reflection spectrum of the micro-cantilever structure measured is 8.8 dB, and the free spectrum range is 7.72 nm. The FP cavity length is 155.6 μm by calculation. Compared with the reflection spectrum of the unprocessed silicone rubber film acoustic sensor, the reflected light is slightly weaker after femtosecond laser processing. However, the reflection spectrum of the micro-cantilever fiber acoustic sensor processed by femtosecond laser can still meet the requirement of acoustic signal demodulation. The acoustic performance of a micro-cantilever beam fiber acoustic sensor is investigated using the orthogonal working point with direct measurement method. By testing the frequency response in the range of 300 Hz to 3 000 Hz, the experimental results show that the sensitivity of the sensor varies in different frequency ranges, with the resonance peak appearing at 2 200 Hz, corresponding to the sound pressure sensitivity of 414 mV/Pa. At 300 Hz, it has the maximum sensitivity of 675 mV/Pa and the sound pressure response linearity of 0.994. Compared with the silicon rubber thin film sensor without femtosecond laser processing, the sensitivity of the micro-cantilever beam acoustic sensor is significantly improved. The first resonance frequency of the cantilever beam fiber acoustic sensor is calculated to be 2 062 Hz, which is close to the resonance frequency of 2 200 Hz measured in the experiment. Meanwhile, the average signal-to-noise ratio of the micro-cantilever beam fiber acoustic sensor is more than 34 dB with the range of 300 Hz to 3 000 Hz. The designed acoustic sensor offers many advantages such as high-sensitivity, simple structure and easy fabrication, which has a wide application prospect in the field of natural disaster monitoring, underwater navigation, sonar positioning, and target recognition.