Abstract: The beam commonly used in engineering has different bending moments on different cross-sections. The material in a beam with uniform cross-section cannot be fully utilized, which is not economical. However, if equal-strength beams are used, the stress on all sections can simultaneously reach the maximum allowable value of the materials so as to fully exploit the load-bearing potential. Accordingly, the material utilization rate is promoted. From the perspective of optimization design, this paper solves the stress on each cross-section along the axis, which is helpful to deepen the understanding of the equal-strength beam design from a general viewpoint.