The spatial resolution of structural vibration modes directly affects the accuracy of damage identification results based on these modes.Digital image correlation (DIC),with its non-contact,full-field measurement capabilities within the field of view,offers a high-density measurement approach.However,limited by the camera's field of view,the DIC method cannot directly perform complete testing on large,slender structures such as pile foundations.To address this challenge,a 3D-DIC stitching measurement-based method for pile foundation vibration mode testing is proposed.The method involves segmented testing to obtain full-field vibration responses of different regions of the pile foundation,uses image feature matching to derive spatial transformation matrices for each region,and achieves the stitching and fusion of full-field modal vibration modes with high spatial resolution.Combined with dynamic fingerprint indicators,the method enables the identification of local damage in pile foundations,and the physical model experiments based on the 3D-DIC stitching measurement method are carried out.The results demonstrate that the vibration modes identified by this approach closely align with finite element simulation results,and provide richer structural detail information compared to traditional acceleration sensor testing.