A temperature-insensitive gas pressure sensor was proposed and experimentally investigated. This sensor was based on a photonic crystal fiber (PCF) sandwiched between two single-mode fibers, where the impact of length on the performance of the sensor has been studied. Air holes of PCF were employed as gas or liquid inlet and outlet channels which provide the medium for direct interaction between the light transmitted in the fiber and the target gases. The experimental results show that the length of PCF has little effect on the sensitivity to gas pressure. The photonic crystal fiber interferometer (PCFI) has a high gas pressure sensitivity of 2.39 nm/MPa when the gas pressure increases from 100 to 900 kPa. The demonstrated gas pressure sensor has excellent stability and reversibility with negligible temperature cross-sensitivity. The proposed PCFI can also be used for liquid sample detection with high refractive index (RI) sensitivity of 3026 nm/RI unit (RIU) when the length of PCF is 1 cm at an RI range of 1.334-1.34. Therefore, the proposed PCFI holds a great potential in applications for chemical gas leakage detection and biochemical sensing.