The supports of plate will be damaged under instantaneous impulsive loads. Dynamic issues of collision between a plate and its supports are equivalent to a problem of plate under uniformly distributed impulse. Based on thin plate theory, thick plate theory and infinite plate theory, dynamic responses of a plate under uniform impluses are analyzed. In the analysis, the effects of shear deformation and moment of intertia on dynamic behaviours of plate (frequence, flexibility and interal force etc) are respectively considered. The results indicated that the deflections calculated under thin plate theory are smaller than those of thick plate theory, and the internal force are much more smaller. Therefore, shear deformation and moment of inertia should must be taken into accounted for the correctly calculation. Besides, the different calculate results between infinite plate theory and thick theory shows that the infinite plate theory can be used for thick plate calculation when the length-width ratio is larger than 5 for the discrepancy of deflections and internal forces is very small on this condition.