Abstract: In order to solve the problem of wasteful use of steel by reference to experience in the design of round pipe belt conveyor joist structure, an optimal design method based on Design of experiment (DoE) is proposed. The design of the steel joist is based on design of experiment (DoE). The load combinations of the round pipe belt conveyor joist are analysed, and the loads are applied in Ansys workbench according to the most unfavourable load combinations of the joist to identify the dangerous bars. Multi-objectives Genetic Algorithms (MOGA) was used to carry out multi-objective optimization. The results show that the overall mass of the optimised truss structure is reduced by 32.8%, resulting in a lighter structure; at the same time, the stress ratios of the bars are increased but meet the strength and stiffness requirements, and the bar sections are more fully utilised.