Abstract: In order to analyze the relationship between the critical load and the buckling shape of a pole bar, on the basis of theoretical analysis and experiments, the method of determinating the critical load through looking for the buckling point for a long slender member subjected to axial compressive force is used in this paper. The critical load can be determined by the longitudinal displacement at one end of the compressive member, which is in equilibrium with a small lateral deflection. The critical load with consideration of the longitudinal displacement is compared to that from Euler's formula, and a larger critical load is obtained.