It is of great importance to predict the vibration energy transmission (structure-borne sound transmission) within rib-stiffened plate structures due to their large applications in practical engineering. Since ribs usually play as junctions between plates, parameter uncertainty effects of the stiffening beams (ribs) on the power transmission between coupled thin plates are particularly addressed based on a plate-beam-plate model. Considering the significant dynamic mismatch between the ribs and plates, the Hybrid FE-SEA Method is adopted during the simulation. Numerical investigations have shown that the variations of the stiffness and boundaries of the beam tend to have relatively much more significant effects than those of the material properties and interface coupling degrees of freedom (DOFs).