This paper modifies and improves the algorithm of sight distance triangle according to the traffic flow and geometric features of intersections. Using the modified crossable intervals and the traffic volume on the secondary road and the obstacles within the improved sight distance triangle as selection criteria, we put forward the control mode selection flow diagram of plane intersections in this paper, hoping to quantize the selection criteria, as well as normalize and visualize the selection process.Finally,this paper checks the accuracy and reliability of the model through the analysis of a case.