Abstract: The inelastic deformation induced by the gap between bolt and hole cause the deflection of bolt connection structures. Based on finite element theory, the gap-existence truss element is proposed to simulate the mechanical behavior of bolt connection structures，which can accurately calculate the structural inelastic deformation of gaps at connection joints, The iterative method based on incremental theory of residual load factor is presented according to the characteristics of gap element. This method provides theoretical basis for the calculation of abnormal deflection of the arch in construction control of Sang Ba bridge in Guizhou province. The calculation result is in good agreement with measured data, proving the method is accurate and practical.