The aerodynamic interference on the adjacent three separated deck bridges in different altitude difference ratios was investigated by CFD and is verified by the wind tunnel test. The altitude difference ratio (H/D0) is within the range of -2 and +2, where H is the difference of centroid height between the middle box beam and the two sides symmetrical composite girders and D0 is the height of the middle box. The numerical simulation results show that the downstream composite beams have an inhibition effect on the vortex shedding of the middle box beams in a certain range of height difference. At the actual spacing in project, the mean values of the aerodynamics of the adjacent three separated deck bridges are interfered with each other obviously and regularly in the range of H/D0 stu-died in this paper. The aerodynamic interference of middle box girder is the largest, that of the downstream girder takes second place, and that of the upstream girder is the least.