To investigate the influence of cable clamp slippage on alignment and internal force of the main cable, a theoretical analysis method based on node coordinates of the main cable after cable clamp slippage was proposed in this paper. Based on segmented catenary theory, the influence of hanger inclination caused by hanger slippage on the horizontal force of the main cable was considered. The segmental cable element of the main cable was equivalently expressed as expressions of hanger tension and unstressed length. With total unstressed length kept constant as a control condition, the horizontal force of the main cable was iteratively updated to solve convergent alignment, segmental unstressed length, and hanger tension of the main cable. By taking a single-tower self-anchored suspension bridge as an example, a parametric analysis was carried out to study the sensitivity of node coordinate error to control condition, and a quantitative analysis on the location and quantity of main cable slippage was conducted. The variation characteristics of internal force and alignment of cable structure after slippage were identified, and the mechanical performance of the structure under slippage conditions was qualitatively evaluated.