The invention discloses a system used for alleviating traffic congestion of a crossing. A primary buffer zone, a secondary buffer zone, buffer zone signal lamps, traffic signal lamps and cameras are arranged at each road of the crossing respectively, wherein an area, less than dm from a stop line, of each road of the crossing is taken as the primary buffer zone, and a fixed traveling direction isnot set for all the lanes in each primary buffer zone; an area, except the primary buffer area, of each road of the crossing is taken as the secondary buffer zone, and a fixed traveling direction is set for each lane in each secondary buffer zone; the buffer zone signal lamps are used for indicating vehicles in the secondary buffer zones to enter the corresponding primary buffer zones; and the traffic signal lamps are used for indicating vehicles in the primary buffer zones to travel and pass the crossing. In the method disclosed by the invention, indication of the buffer zone signal lamps isdecided by the traffic signal lamps and indication of the traffic signal lamps is decided by traffic flow monitored by the cameras provided with a virtual coil, namely the indication of the buffer zone signal lamps, the indication of the traffic signal lamps and the traffic volume monitored by the cameras are in a linked relationship.