<p>Natural gas hydrates can cause pipeline blockage during oil and gas transportation, leading to significant economic losses and environmental risks. Conventional thermodynamic hydrate inhibitors, such as methanol and ethylene glycol, can effectively prevent hydrate formation. However, these inhibitors require to be applied in high concentrations, thus being toxic to humans and the environment. Kinetic hydrate inhibitors (KHIs) have recently attracted attention due to their advantages, including environmental friendliness and the possibility of using lower concentrations. In this article, we carry out a systematic review of research literature on synthetic and natural KHIs, analyzing their inhibition mechanisms, characteristics, and limitations. Particular attention is paid to the experimental studies of urea, a new environmentally friendly inhibitor with both thermodynamic and kinetic action.</p>