Natural gas hydrates were easily generated in the drilling and development of deepwater oil and gas reservoirs，which will have a serious impact on deepwater drilling and oil and gas gathering and transportation. The components of associated gas in a deepwater oilfield were complex，and the existing hydrate formation prediction models had large calculation errors. In order to accurately measure the hydrate formation risk of the associated gas in the oil field，a natural gas hydrate micro-observation experimental device was used to determine the hydrate generation conditions of the multi-component gas in the oil field. The influence of ethylene glycol on the formation conditions of multi-component gas hydrate was explored. The results showed that when the temperature was below 15 ℃，the phase equilibrium condition of the multi-component gas was lower than that of methane and carbon dioxide，and higher than that of ethane and propane. When the temperature was higher than 15 ℃ ，the phase equilibrium condition of the multi-component gas was lower than that of methane，ethane and carbon dioxide，which showed that compared with methane gas，the multi-component gas was easier to form hydrate due to the presence of ethane and propane. In addition，hydrate crystals growed in acicular form，and the acicular structure would rapidly develop into body structure，which would easily cause pipeline clog. When the average pressure of the fluid in the gathering and transportation pipeline was 5 MPa， 40% ethylene glycol solution could reduce the equilibrium temperature of the simulated gas hydrate phase by 5.3 ℃，providing a theoretical basis for hydrate prevention and treatment in the process of underwater oil and gas gathering and transportation in this oilfield.