The invention discloses a diaphragm coupling type extrinsic fiber fabry-perot sensor probe, which comprises a support sleeve, an optical fiber stub installation part, an optical fiber stub arranged in the support sleeve via the optical fiber stub installation part, and an optical fiber arranged in the optical fiber installation hole of the optical fiber stub. A first reflection film is coated onto the front end of the optical fiber stub. The first reflection film at the front end of the optical fiber stub is positioned inside the support sleeve. The front end of the support sleeve is fixedly provided with a second reflection film. The second reflection film and the first reflection film are the same in reflectivity. The second reflection film and the optical fiber stub with the first reflection film together form a fabry-perot cavity. According to the technical scheme of the invention, a fabry-perot sensor is higher in response frequency while being provided with a thinner diaphragm. Therefore, the detection sensitivity of the partial discharge sensor is improved. At the same time, the probe is simple in manufacturing process. During the experiment and investigation process, the trial production of the sensor can be easily conducted.