The invention provides a long-term deformation monitoring method and device, which relates to the field of building structure. The long-term deformation monitoring method includes the following steps:obtaining an image of a pattern on a foundation pile used to monitor whether the foundation pile deforms; and obtaining the deformation state of the foundation pile based on the image. According to the long-term deformation monitoring method and device provided by the invention, a new economical, effective and simple-to-operate scheme is provided for multi-scale deformation monitoring of a complex port wharf structure. Based on the speckle monitoring and image processing technologies, the deformation state of a wharf foundation pile can be monitored for a long term in a non-contact manner. The defect that a wharf cannot work and production is affected due to the fact that loading is needed in the traditional test is overcome.