Aiming at the problem that the vehicles always turn left in advance which causes heavy conflicts in the intersection and effected traffic efficiency, the solution of the left-turn lane’s stop line backwards setting was proposed, and the critical conditions on the stop line’s setting were studied. Firstly, we studied the characteristics of trajectories distribution in the release process of turning left in advance vehicles. Based on that, we proposed to move the stop line backwards to solve the problem of turning left in advance. Considering the intersection’s geometric features and the vehicle operation features, the geometric critical condition was given for setting the position of left-turn lane’s stop line. And then the model of left-turn vehicles’ queuing length was established based on queuing theory and traffic wave theory. By using queuing length model, the flow restrictions of stop line backwards could be found. Assuming left-turn vehicles’ arrival rate is stable in a certain period of time, the minimum green time and the maximum red time of left-turn phase were given after the stop line was set up. According to the changes of the vehicles’ turning paths, the shortest yellow setting recommendation was given. Finally, the application of the critical limits used in stop line backwards setting was demonstrated. The research result could provide a theoretical basis for traffic signs and markings’ setting and perfect the relevant laws and regulations.