Natural gas hydrate (NGH) is characterized as a potential energy resource. The commercial application of hydrate energy requires further development due to the complexity of hydrate exploitation. The particle size significantly affects the exchange ability of gas and water in the pores of the sediment during hydrate dissociation. In addition, sediment deformation during hydrate decomposition is generally correlated with marine disasters and requires further characterization. In this work, different quartz sand particle sizes were applied to simulate the sediment of hydrate reservoir. According to the data analysis, the formation and gas production rates of methane hydrate decreased with sediment particle size due to the difference of the specific surface area. In addition, the sediments exhibited different deformations after the hydrate dissociation. Smaller sediment particle sizes generated more obvious deformations following methane hydrate decomposition.