Abstract:The stress process of a steel box-concrete composite beam is theoretically analyzed and studied, which provides a reference for the design and application of small-span and medium-span steel box-concrete composite beams in China. By contrastive analysis on the closed section and open section of steel boxes, it is found that the closed section increases a little steel amount compared with the open section, but the stress level of the steel beam is reduced and the number of welds is reduced so as to decrease the welding problems, which is suitable for the construction of small-span and medium-span steel box-concrete composite beam bridges.