PA66 with different aged time was characterized by dynamic mechanical analysis (DMA).The mechanisms of DMA analysis were identified with the results of DSC curves and impact strength test. The results indicate that dynamic parameters such as loss tangent, storage modulus and storage compliance have a regular change along with the prolongation of aged time. The maximum temperature of main relaxation loss tangent increases first and then decreases, and becomes stable at the last stage of thermal aging. The storage compliance constantly decreases with the prolongation of aged time. It is a practicable way to characterize the aging-resistant performance of polymer by DMA analysis, moreover the polymers aging mechanism can be concluded according to molecular movement and dynamic parameters.