Abstract: To avoid the air traffic collision,secure the flight safety and improve the air traffic controller’s capability to foresee and deal with flight conflicts,a radar-based coordinate system was established,and the concept of "horizontal detection" to foresee multi-traffic flight conflicts was brought forward.Furthermore,a method to foresee the horizontal detection of multi-traffic flight conflicts and the time slice of conflicts was proposed.The research shows that if the protected zone of aircraft Ai is intercrossed with the shadow of aircraft Aj on a horizontal surface and there is a vertical conflict,a flight conflict between aircraft Ai and Aj will occur.Under this condition,it is advisable to adjust the aircraft heading and speed or alter the flight altitude to avoid the flight conflict with the help of a surveillance radar.However,if there is no intercross in the time slice of horizontal and vertical conflicts,no flight conflict will happen between aircraft Aiand Aj.Finally,a simulation analysis was made to test the validity of this method.