Abstract: In order to realize the sensor based on all-solid bandgap optical fiber, a mode interferometer based on two-taper structure was introduced. Using a splicer to fabricate an all-solid photonic bandgap fiber modal interferometer by concatenating two tapers separated with a middle section of the fiber. Compared to the conventional fibers or the index-guiding photonic crystal fibers as previously presented, the all-solid bandgap optical fiber have a lower effective index in the core and a higher effective index in the cladding. According to the theoretical analysis and experimental verification, we measured the temperature response and the axial stress response of our structure. The measured sensing sensitivities are~63pm/oC for temperarure and ~-1.74nm/N for the axial stress, respectively. The Analysis shows that a two-tapers modal interferometer based on all-solid photonic bandgap fiber has a much compact device size and a simple fabrication compared to the long-period grating and the Bragg grating, which has wide range of potential applications in optical sensing fields.