In order to analyze the traffic congestion problem of roundabout, the irregular roundabout of Dalian dig-ital square is taken as an example, the arrival time and space and velocity distribution characteristics of the en-trance traffic flow are analyzed by the measured data, and the traffic congestion of the intersection is simulated and analyzed by Fluent fluid. The results show that the traffic flow at the intersection entrance has little to do with time, and is related to the geographical location of the intersection. Among them, the arrival and departure traffic flow at the entrance of the morning peak hour obeys the negative binomial distribution, and the speed at the entrance of the morning peak hour obeys the Weibull distribution. The congestion at the roundabout mostly occurs at the entrance and exit of the intersection, and the congestion in the short weaving area is more serious than that in the long wea-ving area. When the inner diameter is increased from 50 m to 65 m, the weaving angle is decreased by 8°, the pressure in the ring is decreased by about 25.6 %, and the minimum speed is increased by about 464 %. When the inner diameter is increased from 65 m to 80 m, the weaving angle is decreased by about 4°, the pressure in the ring is decreased by 20.2 %, and the minimum speed is increased by about 62 %.