Abstract: The dynamic mechanical properties of viscoelastic material embedded in composites and that co-cured with composites was investigated by dynamic mechanical thermal analysis (DMTA). The effects of co-curing process, the thickness of viscoelastic layer and the composite flexible layer on the damping characteristic of co-cured composites was studied by finite element method. The results show that, the value of damping crest is 54% of idealized value due to the interaction of the resin and the embedded viscoelastic material during the process of co-curing. Increasing the thickness of the embedded viscoelastic layer or inserting some flexible layers near the viscoelastic layer not only results in the increasing the value of damping crest of co-cured composites but also can widen the temperature range of damping in co-cured composites.