Abstract: To investigate the aerodynamic characteristics of train-bridge systems in a complex traffic condition, a section model wind tunnel test was carried out for a long-span rail-cum-road cable-stayed truss bridge. The tri-component forces on the train-bridge system were measured under different angles of attack when a single train, two trains or three trains passed. The effects of the track positions, bridge towers, road traffic flows, meeting of the trains on the tri-component coefficients of the vehicle and the truss were studied. The results show that when a train moves from the windward track to the leeward, the drag coefficients of the vehicle and the truss gradually decrease, while the lift coefficient of the vehicle and the moment coefficient of the truss reach the maximum on the leeward track. As a train passes through the tower, the average surface wind pressure of the shielded vehicle is significantly reduced, and the shielding effect is most obvious when it is on the windward track. However, the surface wind pressure near the tower edges remarkably fluctuates. When two trains meet on the bridge, the drag and lift coefficients of the vehicle increase with the meeting spacing. When three trains meet on the bridge, the drag and lift coefficients of the vehicles behind the windward train significantly decrease. The middle train has the smallest lift coefficient and a negative drag coefficient. As the number of trains on the bridge increases, the drag and lift coefficients of the truss gradually increase, while the moment coefficient remains almost the same.