| In order to mitigate the traffic congestion around the off-ramp，the speed harmonization control method of main line is proposed. Based on existing section-based speed harmonization model, a lane-based speed harmonization model was designed with factors of on-ramp and off-ramp. The model can describe and forecast the traffic state, and give the optimal speed on each lane with shortest travel time as well as maximum total through traffic volume. Finally, the simulation system was developed to scientifically evaluate the effectiveness of lane-based and section based speed harmonization model in different traffic demand situations. The simulation results indicated that, speed harmonization strategy is more adaptive for medium and high traffic flow density. When traffic demand is high, both of lane-based model and section-based model can reduce the vehicle average delay compared to no control strategies, and in most cases, the lane-based speed harmonization model is superior to the section-based model, which is helpful to mitigate traffic congestion and improve traffic safety.