The invention provides a method for observing the layered deformation of deep parts of foundations. The method adopts an observation mode combining shallow punctuation with deep punctuation, which can observe the deformation of a surface layer and a shallow layer of an experimental foundation, carry out layered observation to the layered deformation of the deep part of the foundation and accurately observe the layered deformation of the deep part of the foundation. The method can achieve the aim of omni-directionally observing the experimental foundation, and can accurately capture the horizontal and vertical deformation range of the foundation and determine the lower limit depth of collapsible loess, so as to provide powerful technical support for determining foundation treatment depth, treatment range and the negative friction range of a pile foundation.