A micro rectangle hole is ablated in a photonic crystal fiber by using 157 nm excimer laser pulses to form a fiber Fabry-Pérot cavity (PCF F-P), because the 157 nm excimer laser used in micromachining has high single-photon energy, high peak power, high absorption coefficient and high resolution. The PCF F-P cavity with a length of ～45.6 μm has obtained a smooth interference fringe and an excellent fringe visibility of ～26 dB. An explanation for the formation of such a high quality cavity is presented based on the interaction mechanism between the laser and silica material. This PCF F-P is used for measurement of strain and a sensitivity of 0.32 nm/μm and a linearity of 0.9994 within a range of 550 μm are obtained. Furthermore, it is verified that the PCF F-P sensor is insensitive to temperature change as the cavity length only changes 20 nm for a temperature range of 800 ℃. Such a fiber Fabry-Pérot cavity is fabricated easily and formed straightforwardly with high efficiency and precision, leading to the possibility of mass production of high-quality PCF F-P cavities then extensive applications.