Abstract: Taking the example of simply-supported beams under uniform load, the elastic analysis of the effects of web opening and stiffening method on the steel beam was conducted. The analysis revealed that:the increment of deflection due to openings was a trilinear curve, the openings at mid-span had little effect on the defection of the beam; when the openings with the same size were eccentrically positioned, the deflection increment was smaller, the stresses in the opening segments were also smaller;however, the opening had a significant effect on the local buckling of the web. After analysis,an equation for the increased deflection of simply-supported beams was proposed;the width-to-thickness ratio of the unstiffened opening should be limited.For the sizes of the openings in high-shear or low-shear segments, the British SCI regulations were introduced for reference; the openings in high-shear segment had significant effect on the strength and local buckling of the beam, it was suggested that horizontal stiffeners should be used to avoid local buckling and increase the strength.