To maximize the number of vehicles passing by the stop-line in a cycle and improve the operation ef-ficiency of intersection in China, the settlement of left-turn lane waiting-zone is becoming prevailing. Based on conflicting-point method, the internal mechanism of left-turn flow after stopping line was analyzed through taking postposition left-turn lane waiting-zone intersection for instance. The relationship between the first left-turn vehi-cle and the last vehicle of previous phase passing the conflicting point was expounded. According to the time of successive arriving of two vehicle flows at conflicting-point, the reasonable layout for waiting area of left-turn ve-hicles was researched when the clearance index was less than O. The results suggest that the appropriate layoutfor waiting area of left-turning vehicles can improve the operation efficiency of intersections.