The invention discloses an optical fiber Fabry-Perot ultrasound hydrophone and a system, which are used for measuring an HIFU (high intensity focused ultrasound) sound field. The system comprises a light source assembly, an optical fiber assembly, the optical fiber Fabry-Perot ultrasound hydrophone, a clamp, and a detection and feedback assembly, wherein the clamp is used for clamping the optical fiber Fabry-Perot ultrasound hydrophone, light emitted by the light source assembly reaches the optical fiber Fabry-Perot ultrasound hydrophone through the optical fiber assembly, the reflected light of the optical fiber Fabry-Perot ultrasound hydrophone, which is modulated by ultrasound, passes through the optical fiber assembly, and is received and processed by the detection and feedback assembly, the optical fiber Fabry-Perot ultrasound hydrophone comprises a single-mode optical fiber, a reflecting optical fiber and a quartz capillary tube, the two ends of the quartz capillary tube are respectively connected with the single-mode optical fiber and a reflecting optical fiber, and an air cavity in the quartz tube is an interference cavity. The optical fiber Fabry-Perot ultrasound hydrophone and the system have the advantages that the high sound pressure of the HIFU sound field can be borne, the sound pressure sensitivity is high, the space resolution is high, and meanwhile, the temperature is measured.