Abstract: Methane (CH₄) cracking directly produces hydrogen and solid carbon, representing a promising hydrogen production route with low carbon emission potential. However, conventional solid catalysts are prone to deactivation due to carbon deposition, which limits continuous operation. Owing to their excellent fluidity, high heat-transfer efficiency, and inherent capacity for carbon separation, liquid metals offer a promising reaction medium for continuous methane cracking. In this study, molten tin (Sn) was employed as the reaction medium. Bubble chemical vapor deposition (BCVD) experiments were conducted at 1273-1373 K with methane inlet concentrations of 10%-100%. Combined with computational fluid dynamics (CFD) simulations and a plug-flow model, the methane cracking behavior and carbon product formation mechanism were investigated. The results show that methane conversion ranges from 2.3% to 22.5%, increasing with reaction temperature and decreasing with methane concentration. At low methane concentrations, the carbon products primarily consist of thin, wrinkled graphite flakes, and higher temperatures enhance their degree of graphitization. At high methane concentrations, the formation of particulate carbon black is favored, accompanied by increased structural disorder. Apparent kinetic analysis reveals that the lowest activation energy, 156.11 kJ·mol⁻¹, occurs at 10% methane concentration, indicating that the molten Sn interface exhibits a catalytic effect on methane cracking. These findings provide guidance for optimizing liquid-metal -catalyzed methane cracking and the controlled synthesis of high-value carbon materials.