Abstract: In order to find out the horizontal axis offset law of mortise segments caused by grouting loading of tunnel shield, the causative factors of mortise segments uplift caused by back-filled grouting are analyzed by taking a small curvature radius shield tunnel as an example. Considering the deformation of "ellipticization" of segment rings, pre-stressing of longitudinal connecting bolts, the influence range of ring joints and transverse stiffness, established was the calculation formula for longitudinal equivalent bending stiffness of segment unit with mortise ring joints under mortise connection conditions. By calculating the static and dynamic uplift force of the mortise segments under the shield grouting loading, constructed was the expression for the uplift force of the mortise segments under the shield grouting loading. Based on this, analyzed were the force on the mortise segments under shield grouting loading in small curvature radius tunnels and its deflection and deformation law under the assumption of Winkel's elastic foundation beam, and established was the calculation approach for the horizontal axial offset of the mortise segments under the shield grouting loading. And it was verified upon the practical engineering. The results show that the theoretical values in this study fit well with the simulated values and monitoring values. The calculation approach of this study can be suitable for practical engineering well. It can provide an effective theoretical guidance for segments offset and misalignment under grouting loading in shield tunneling project and similar projects.