Abstract: Clarifying the impact of pass topographical factors on the icing of transmission lines in pass is crucial for the differential anti-icing of transmission lines in mountainous places. Based on the anti-terrain theory in hydrological analysis, the mountainside pass is initially suggested in this work, and a numerical model of the pass wind field is established. The model is then verified by wind tunnel test. According to the distribution of the pass wind field, the erection paths of three types of pass transmission lines are selected, and the wind speed range of the pass transmission lines is obtained. In the initial state, the thickness of the single ice coating on the wire should not exceed 7% of the wire diameter as the basis for the value of the ice-covering step. The flow field, particle transport model, and thermodynamic equations are cycled through calculations to determine the icing situation of the wire in the wind speed range. Then the ice load curve of the pass line is obtained. In the sag region of the line, the ice load curves of the mountainside, mountains, and mountain pass, respectively, have bending, falling, and concave trends. The pass line's natural icing experiment validates the accuracy of the ice model and confirmes the uneven icing over the pass line, and the law of uneven icing and the computed ice load curve are similar. The ice load curves of three types of passes under different combinations of pass topographic factors are calculated, and the concept of maximum stress ratio is proposed as a criterion for judging the possibility of line accidents caused by ice coating. The relationship between different pass topographic factors and the maximum stress ratio of the pass line is quantified.