Abstract: To explore the characteristics of traffic flow in the expressway reconstruction and expansion work zone, combined with the measured data and simulation analysis, based on the speed, flow and saturated headway of different lanes in different control sections (warning zone, transition zone and working zone) of the work zone, the change of traffic flow parameters and the interaction of traffic flow between lanes were analyzed. The research shows that the transition zone is the bottleneck of traffic operation in the work zone, in different control sections, when the density is greater than 30 veh/km, the traffic flow state changes suddenly; in different lanes, when the density is greater than 15 veh/km, the inner and outer lane traffic flows exhibit different characteristics. Based on the velocity-flow observation and simulation data, a regression model was established. The analysis results show that before and after traffic interruption, the percentage of decrease of flow rate in 2-1 work zone and 3-2 work zone is 8.56% and 9.25%, respectively. According to the traffic flow characteristics of the work zone, the capacity of the work zone is defined as the queuing flow rate, and the calculation method of the capacity is given. The capacity of 2-1 construction area and 3-2 work zone is 1 610 veh/h and 3 650 veh/h, respectively.