Abstract: Traditional catalytic combustion methane sensors used in underground coal mines are susceptible to sulfur poisoning and require an oxygen-enriched operating environment. By contrast, infrared and laser-based sensors generally suffer from high power consumption, making it difficult to simultaneously satisfy the requirements of long-distance wireless transmission and EPL Ma level (the highest equipment protection level) explosion-proof standards. This limits their application in high-risk areas such as mining working faces and goafs. To address the above problems, a novel mine-used methane sensor based on graphene-enhanced D-shaped photonic crystal fiber surface plasmon resonance (PCF-SPR) is proposed. Graphene thin films are deposited on the polished flat surface of the D-shaped fiber to excite the surface plasmon resonance (SPR) effect, which significantly improves the gas detection sensitivity. The finite element method is adopted to systematically simulate and analyze the effects of air hole diameter, air hole spacing and TiO₂ coating on the optical loss of the fiber, and the correlation between the refractive index (RI) of the measured gas and sensor sensitivity is investigated. The simulation results show that the designed sensor achieves an excellent spectral sensitivity of 17 200 nm/RIU. When the refractive index of methane ranges from 1.42 to 1.44, the sensing resolution reaches 5.8×10⁻⁶ RIU, which meets the high-precision detection requirements for methane in underground coal mines. Benefiting from the chemical stability of graphene and the intrinsically safe passive characteristics of optical fibers, the proposed design features explosion-proof safety, moisture resistance, dust resistance and electromagnetic interference immunity, and realizes high-sensitivity as well as long-distance distributed detection simultaneously.