Abstract: The element stiffness and mass matrices for the stiffened composite laminated plate is derived based on Mindlin deformation assumption. A damping model is constituted by using Rayleigh damping model in conjunction with Adams' strain energy method (MSE). A three-plate model for describing the delamination and a multi-scalar model for describing the micro-cracks damage are established. To avoid the overlap phenomenon between the upper and lower sub-laminates at the delaminated region during dynamic analysis process, a nonlinear interface element is constructed according to Hertz contact law. A precise time-integration method is used to calculate the dynamic response analysis for the damaged stiffened composite plate. Numerical results show that the interaction between the imbedded delamination and the induced matrix's crack during the dynamic process affects the dynamic response of the stiffened composites plates significantly.