Abstract: I-rib stiffened plates are the basic components of steel boxes, steel arches, steel toweres and steel pieres in bridge structures.The stability of stiffened plate under compression is the focus of steel bridge design.To study the overall stability performance of stiffened plates, I-rib stiffened plate specimens with different geometric dimensions were designed for an axis compression test.The initial geometric imperfections of specimens were measured, and corresponding finite element models were established.The effects of the constitutive relationship, residual stress, and initial geometric imperfections were considered.The stability reduction coefficients were obtained by massive numerical calculations and compared with national codes.Analytical results show that the imperfections of the specimen are high in the middle and low on both sides along the plate width, and have randomness in the initial bending direction.For the medium and long column specimen, bending instability deformation occurs in the middle of the specimen, and the ultimate bearing capacity of the stiffened plate side bending is higher than that of the stiffener side.For the short column specimen, the out-plane-buckling deformation occurs in the middle of stiffened plates and stiffeners end.With the increase of slenderness ratio, the instability characteristic of axial average stress-displacement curve for the specimen with stiffened panel side bending is more obvious.The stability coefficients of test and finite element model are higher than the class B column curve in the Chinese steel bridge code.Using the class B column curve in the Chinese code for calculation is safe.