Abstract: There is a significant resistivity difference between the gas hydrate and the sea-floor sediment. Measuring the electromagnetic anomaly caused by the resistivity difference below sea-floor can contribute to detecting the layout and saturation of target gas hydrate reservoir. We build several one-dimensional resistivity models with gas hydrate reservoirs having different porosity and saturation. Using the models we investigated the electromagnetic anomaly caused by gas hydrate reservoirs and the feasibility to detect gas hydrate by using time domain marine CSEM method.