Abstract: Experiments are conducted on sixteen specimens of simply supported composite steel-concrete beam with compact steel section to investigate their behavior of shear resistance. Above all, the vertical shear resisted by joist is calculated to investigate the vertical resisting shear capacity of shear force components of composite beams in experimental research on composite shear behavior of steel-concrete composite beams under sagging moment. In this paper, one method on stress analysis of webs of steel joists is introduced to compute shear stress in plastic range, and this method can estimate whether the stress state of steels is within strain-hardening range. Experiments were conducted on two specimens of steel beam with same section to validate this method. Test results show that the calculating results of this method agree with the collected data well.