Abstract: Under the excitation of harmonic force the vibrational power flow characteristics of plate with a surface crack are investigated from the view of structure-borne sound. The presence of the crack introduces the discontinuity of rotational displacement between the two sides of the crack, and the additional angle is deduced from fracture mechanics. According to the boundary conditions at the locations of force and crack, the flexural wave motion in the cracked plate is deduced，then the input power flow and the transmitted power flow in the cracked plate are calculated. The comparison between the power flow in intact plate and that in cracked plate shows that the presence of crack changes the power flow characteristics. The characteristic parameters of crack can be derived from the input and transmitted power flows. In the end, the contour lines of input power flow are constructed to identify the crack in the plate.