In order to achieve high precision gas pressure measurement,an optica l fiber Fabry-Perot interferometer (FPI) gas pressure sensor is proposed by femtosecond laser microm achining technique and optical fiber splicing technique.A micro hole is fabricated on a capillary quar tz tube by femtosecond laser pulses with a wavelength of 800nm.The capillary quartz tube is connected betwe en a segment of single-mode fiber (SMF) and a segment of multimode fiber (MMF) by optical fiber splicing technique to prepare an optical fiber gas pressure sensor.By changing the gas pressure in FP cavity of the sensor,the refractive index of the gas in FP cavity will change,and the transmission spectr um will shift linearly.The pressure change in the cavity is observed by a barometer,and the sensitivity of the sensor is calculated by changing the relation between the variation of the barometric pressure and the w avelength shift.The operation mechanism of capillary pore structure for gas pressure measurement is analyzed theoretically. The sensitivity of the sensor is measured by the change of ambient gas pressure and temperature.The experimental results show that the ambient pressure and temperature have influen ce on the sensor head,and the pressure sensitivity is 4.22nm/Mpa.The temperature sensitivity is far less t han the pressure sensitivity,so the design sensor can eliminate the cross-sensitivity of ambient temperature an d gas pressure.