Abstract: To mitigate the depletion and contamination of freshwater from hydraulic fracturing, in-situ methane explosive fracturing technology has been emerged. The foremost challenge is how to design the combustion improver formulation that induces methane to generate a violent detonation and thus fracture shales. A mixing scheme of ignition (propylene oxide and oxygen) and combustion improvers (Ba(NO₃)₂, KMnO₄, NaClO₃ or NaClO₄) was employed to address the formation and sustainment of methane detonation, and initially enhance the explosion characteristics. In a 502.4 L pipeline explosion setup, the contribution of additives to methane detonation was explored, and an optimal formulation was determined. It is revealed that ignition improvers can enhance the energy of methane explosion and accelerate combustion to induce deflagration-to-detonation, whereas combustion improvers can further boost the impact and propagation properties of detonation waves. The most effective NaClO₄ ultimately enhanced the overpressure and velocity of methane detonation by 281.4% and 117.2%, respectively.