Natural gas hydrate represents a significant clean energy resource, whose formation and distribution are critically controlled by sediment heterogeneity. While electrical resistivity tomography (ERT) technology effectively detects hydrate-induced resistivity anomalies, current understanding is heavily biased towards sandy systems, with fine-grained muddy sediments remaining poorly characterized. Utilizing a self-developed ERT experimental system, this study conducted multi-cycle hydrate formation experiments on representative the South China Sea sediments: sea sand and clayey silt. The representative results reveal fundamentally distinct hydrate formation and evolution patterns governed by sediment type. In sea sand, pore water prevents gas from entering pore, leading to localized hydrate enrichment near the gas source. However, the fracture network in muddy sediments is conducive to methane migration, allowing hydrates to form at greater distances. Sediment heterogeneity dictates hydrate distribution and evolution by controlling pore structure and gas-water behavior. Moreover, within the pore space, hydrate growth follows a selective pattern driven by methane concentration gradients, with areas rich in methane supply becoming focal points for hydrate formation. This study elucidates the core-scale evolutionary characteristics of hydrate formation in heterogeneous marine sediments via ERT visualization. The identified distinct resistivity signatures and formation mechanisms provide a critical basis for interpreting hydrate occurrence, formation and exploration.