Bragg fiber is one kind of microstructure fiber with one-dimensional photonic crystal layer in its fiber cladding. In this paper, the hollow-core Bragg fiber for trace gas detection, with a transmission band in the mid-infrared band, is designed and fabricated based on semiconductor glass and polymer materials. The measurements of the fiber sample demonstrate its bandgap-guided properties, showing two obvious bandgap guided transmission bands. The central wavelength of the lowest transmission band is 4.4 μm.