A reasonable left -turn waiting area setting can greatly improve the capacity of the left -turn lane. Firstly, the conditions and effects of left-turn waiting area setting are explored under different traffic saturation of left-turn lanes. Secondly, the capacity model of left-turn lane is modified considering the factors such as the capacity of waiting area, change interval and the microscopic characteristics of the vehicles. Finally, the above modified model is verified by traffic survey and VISSIM simulation. The results show: 1) The left-turning waiting area channelization is beneficial to the improvement of the left-turn lane capacity, but with the increase of traffic saturation, the effect is smaller and the maximum queue length is larger; 2) Through VISSIM simulation, the error of the capacity model can be controlled below 2% considering the influence of factors such as the waiting area capacity.