Abstract: Statically indeterminate tension-compression problems are among the most challenging topics in the teaching of mechanics of materials. The primary difficulty lies in formulating the supplementary deformation compatibility equations. The small deformation magnification graph is usually used in existing text books to derive the equations, which are problem-dependent and hard for students to master. This paper presents a novel method using the compatibility condition of nodal displacements and their relationships between the axial deformation of bars. The theorerical framework of the method is introduced, and three examples are given to demonstrate the implementation process. Compared with the conventional methods, the proposed method is easier to understand and apply, serving as a general method for establishing the compatibility condition of deformations in statistically indeterminate systems.