To investigate hydrate plugging processes and hydrate plugging mechanisms, a high-pressure flow loop was newly designed and constructed where hydrate plugging experiments were performed from natural gas+diesel oil+water systems for a range of water cuts (30-100%) and initial liquid flow rates (1600-2400 kg h(-1)). Based on the experimental data of hydrate morphology and flow parameters, hydrate formation and distribution characteristics in the flow loop were analyzed and two hydrate plugging processes together with the corresponding hydrate plugging mechanisms were proposed. For gradual hydrate plugging, the plugging process can be divided into four stages. Formation and growth of a hydrate deposition layer is the governing plugging mechanism. For rapid hydrate plugging, the plugging process can also be divided into four stages. Liquid stratification and a sharp increase in viscosity is the governing plugging mechanism for rapid hydrate plugging. In addition, silt-like hydrates and flocculent-like hydrate deposition layer were observed in gradual plugging experiments, whereas slurry-like hydrates with no obvious deposition layer were observed in rapid plugging experiments.