The difference of the mechanical performance between the whole bridge pylon and the segment model are analyzed in theoretical method to provide theoretical support for the full-scale segmental model test study. Firstly, choose the most representative full-scale segment in anchorage zone of bridge pylon. Secondly, select the whole model composed of several segments. Finally, analysis the stress distributions in two models under the working load and the cracking load. In the coordinate segment position, stress distribution under design cable force in whole model and full scale segment model is almost the same. It indicates that the working performance of the anchorage zone in the bridge pylon can be studied through the full-scale segment model test.