Abstract: According to the discussion of neutral axis position in mechanics of materials, the influence of neutral axis position on the buckling load of the beam under axial compression is studied. Using the axial static equilibrium equation and the bending equation, the expressions of the offset of neutral axis and centroid axis of the beam with circular section and rectangular section are derived respectively, and the buckling load formula of the beam under axial compression is obtained. The numerical example analysis shows that the neutral axis of the beam no longer coincides with the centroid axis under axial compression, and the neutral axis shifts, and increased with the decrease of the span to height ratio of the beam. However, the offset of the neutral axis of the beam is very small, so the influence on the moment of inertia of the beam is so small that the buckling load of the beam is not significantly affected and could be ignored.