An all-silica Diaphragm-based miniature optical fiber pressure sensor based on the Fabry-Perot (FP) interferometric principle is proposed. The FP structure is composed of a single-mode fiber and a fiber capillary end face diaphragm by a CO2 laser welding. The fabrication process and parameter control of all-silicon diaphragm are introduced in detail, and the pressure performance test system of FP is set up. The experimental results show that the fiber optic FP sensor has good sensitivity and linearity to air pressure, the sensitivity can reach 9.48 pm/kPa when the pressure ranges from 0 to 200 kPa, and the linearity is 0.998. All-silica diaphragm-based fiber FP pressure sensor fabricated by CO2 laser melting capillary end face is more compact, easy to produce, and has great potential in the extreme harsh environment.