Gas hydrates typically exist in two filling forms within natural environments: pore- filling and fracture- filling. Different hydrate occurrence forms exhibit distinct rock physics properties, making their accurate discrimination crucial for a resource assessment and development. Velocity, density, and resistivity are commonly used parameters reflecting hydrate physics characteristics. This study utilizes a rock physics- based numerical model to simulate the influence of hydrate volume fraction on P- wave and S- wave velocities, density, and resistivity in hydrate- bearing sediment. It was observed that, at equivalent hydrate content, fracture- filling hydrate sediments exhibit slightly lower P- wave velocities, significantly reduced densities, and markedly higher resistivity compared to pore- filling sediments. This study constructed a discrimination chart based on these distinct geophysical signatures. Applying this chart to a case study of gas hydrates in the South China Sea demonstrated strong matching between actual data and theoretical predictions. The chart successfully identified hydrate occurrence forms and calculated the saturation of fracture- filling hydrates, proving effective for discriminating and estimating the resource quantity of fracture- filling gas hydrates in the South China Sea.