Photonic crystal fiber gas detection technology is of particular interest for developing a compact， low power consumption， and intrinsically safe laser absorption spectrum gas detection system. First， by optimizing the structural parameters of photonic crystal fibers， over 90% of the optical field modes can be bound near the fiber core， and the relative gas detection sensitivity can be increased to more than 60%. Further， the limitation loss is reduced to 10^-8 dB/m. To obtain higher relative detection sensitivity and lower optical loss， the optical mode can be optimized by adjusting the core microstructure parameters and the array arrangement of the cladding photonic crystal air holes. Then， the gas detection technologies of the end reflection type， fiber grating wavelength modulation type， and different fiber composite types are analyzed. However， it is difficult to ensure the efficient exchange of gas molecules. Combined with special fiber structures such as Bragg grating and long-period grating， an optical resonator can be constructed to effectively enhance the absorption path of optical signal and gas molecules. The design of a composite optical fiber gas probe with different types of optical fiber and gas sensing materials significantly optimizes the selectivity and sensitivity of gas sensing. The optical path can be increased effectively by expanding the optical fiber to > 1 m or using the ring embedding method， resulting in a detection limit up to the ppb level. Moreover， the introduction of erbium-doped fiber can effectively compensate for the optical loss in the fiber ring. Finally， the gas detection performance and future research direction of the porous ring and grapefruit photonic crystal fiber with a large hollow core diameter are analyzed. In the future， to provide technical support for the development of real-time monitoring instruments for hazardous gases in metallurgical and chemical industries， it is necessary to research the performance optimization， system integration， and environmental adaptability of photonic crystal fiber gas laser absorption detection technology.