In this paper, a highly sensitive optical fiber sensor based on the Vernier effect is demonstrated for gas pressure sensing. It consists of two paralleled Fabry-Perot interferometers (FPIs), which are both produced by splicing a single-mode fiber to a short segment of capillary tube, acting as sensing cavity and reference cavity, respectively. The lateral wall of the sensing FPI is drilled with a micro-channel allowing gas to flow in. Due to the small optical path difference between the two FPI, the Vernier effect is caused in the reflected spectrum of the sensor. Thus, the gas-pressure sensitivity is significantly enhanced, achieving up to ~64 pm/kPa which is ~16 times higher than that of a single FPI. Additionally, experimental results show that the sensor is insensitive to the surrounding temperature, which reduces the influence of ambient temperature on the measurement of gas pressure. The advantages of robust structure and high sensitivity of gas pressure indicate that the demonstrated sensor has a promising potential in industrial production, gas detection, and other fields.A highly sensitive optical fiber sensor based on the Vernier effect is demonstrated for gas pressure sensing. It consists of two paralleled Fabry-Perot interferometers (FPIs), which are both produced by splicing a single-mode fiber to a short segment of capillary tube, acting as sensing cavity and reference cavity, respectively. The lateral wall of the sensing FPI is drilled with a micro-channel allowing gas to flow in. Due to the small optical path difference between the two FPI, the Vernier effect is caused in the reflected spectrum of the sensor. Thus, the gas-pressure sensitivity is significantly enhanced, achieving up to ~64 pm/kPa which is ~16 times higher than that of a single FPI. Additionally, experimental results show that the sensor is insensitive to the surrounding temperature, which reduces the influence of ambient temperature on the measurement of gas pressure. The advantages of robust structure and high sensitivity of gas pressure indicate that the demonstrated sensor has a promising potential in industrial production, gas detection, and other fields.