The finite element model of co-cured stitched damping composite （CSDC） square plates is established. The dynamic properties of CSDC are studied by finite element numerical simulation method. The validity of the simulation method is verified by comparing the experimental results with the simulated data. Through the verification of the finite element simulation model， it can be obtained that the first-order modal frequency of the CSDC square plates decrease and the first-order loss factor increase with the increase of the stitch length or the line spacing. The first-order modal frequency and the modal loss factor of the CSDC square plates increase as the damping layer thickness increases. When the total damping layer thickness is constant and the number of damping layers is increased， the modal loss factor of the structure can be improved effectively. The practical significance of this result is that the resonance phenomenon can be avoided by changing the parameters of the CSDC， which lays a foundation for the wide application of CSDC.