In order to enhance the bearing capacity of structural components, save materials, and reduce cost, a glued laminated timber (glulam) I-beam that is theoretically suitable for engineering application was proposed. In this study, 18 glulam specimens were fabricated using larch dimension lumber and resorcinol–formaldehyde resin. Four-point bending tests were carried out to compare the ultimate bearing capacity, strain, and deflection of various specimens. The results showed that: (1) The typical failure mode at bending is the web shear failure parallel to grain. Before the failure, cracks and sounds appear at the beam web, which represent the sudden brittle failure. (2) The cross-sectional strain of glulam beam changed linearly with the beam height, indicating that the plane section assumption was basically established. (3) Stiffener could improve the initial flexural stiffness of glulam beam, which experiences an increase of 28.21%. Larger the shear span ratio, smaller the initial flexural stiffness. The initial flexural stiffness improves by 10–23.5% with the increase in the thickness of the lower flange. (4) The effects of stiffener and shear-span ratio on shear strength are relatively significant. After the stiffeners are set at the support and the loading point in pairs, the shear strength of the glulam beam increases by 15.05% averagely. With the increase in the shear-span ratio, the shearing strength of the glulam I-beam gradually reduces. The equation of the shearing strength with the shear span ratio is obtained, which is shown by high fitting precision. (5) The shear strength correlation, as proposed by Soltis and Rammer, is suitable not only for rectangular beams, but also for glulam I-beams.