The invention discloses a damping parameter optimization method of a steel plate composite beam bridge and a damping restraining device, which relate to the technical field of bridge structures. The method comprises the following steps: S1, obtaining vibration damping force calculation data and seismic damping force calculation data, wherein the obtained calculation data include a bridge mass matrix, a bridge damping matrix, a bridge stiffness matrix, a displacement, a velocity and an acceleration in a spatial direction, a velocity index and an external excitation load; S2, obtaining a generallateral damping force according to the lateral data, a general longitudinal damping force according to the longitudinal data, and a general vertical damping force accord to the vertical data; S3: obtaining the spatial included angle, damping force and damping parameter according to the data in S2. The invention improves the vibration damping and anti-seismic capability of the light-weight steel plate composite beam bridge.