Abstract: The scaled test of single span double-layer braced frame structure presented in this paper focuses on the influence of initial geometric imperfections on the deformation property. The test results and the finite element analysis results are in good agreement, which proves the correctness of the finite element model by taking random initial imperfection into consideration. A great deal of full-path analysis of 32-story three-span steel braced-frame structures with random imperfections is carried out by using the finite element program ANSYS. The distribution of random initial imperfections is achieved by employing Monte Carlo method and Latin hypercube sampling technique. In addition, the deformation properties of the structure and components were analyzed emphatically, comparing with some methods of the standards at home and abroad. The results show that the defect simulation calculation values of lateral drifts are close to those for ideal frames without any initial imperfections. It could be neglected in advanced design for slender flexible structure. The specification of the frame designed by the Chinese standard is far beyond the framework of random defects because the additional horizontal force exaggerates the detrimental effect of defects.