Numerical simulation and experimental research were carried out on the flow field characteristics of gas-liquid separators with vortex hoods of different lengths under the condition of flow pulsation.When the covers column length is 39 mm,the separation performance of the cyclone is the best.The separation efficiency reaches 95%.And as the length of the column section of the cover increases,the separation efficiency of the cyclone decreases;the separation efficiency is the worst without a cover.And the flow field is extremely unstable.The separation efficiency fluctuates with time.High-speed camera and indoor test system were used to do the experimental research.High-speed camera was used to observe the gas core shape in the swirling field.The indoor test system was used to measure the separation efficiency.The test efficiency is slightly lower.The error is within the acceptable range for the simulation efficiency.Origin software was used to fit the length of the column section to its separation efficiency.And the relationship expression was obtained.The correlation coefficient R2 is as high as 0.99.The swirl strength S was used to describe mathematically the flow field shape and the relation between the length of the column section and the swirl strength was obtained.