Characteristics of meridional movement of western Pacific subtropical high (WPSH) ridge lines at different heights under the influence of a single tropical cyclone (TC) ——Megi and its possible mechanism are analyzed by conducting sensitivity experiment with WRF. The results show that the WPSH ridge lines shift southward under the influence of TC Megi. Furthermore, the higher the ridge lines are, the more southward they move. The possible mechanisms are that the shift of WPSH ridge is directly affected by the zonal wind anomalies in its vicinity regions, and the zonal wind anomalies and temperature anomalies near the ridge line caused by TC Megi activities generally satisfy the thermal wind relationship. Therefore, when the temperature gradient anomalies near the ridge line are positive under the influence of TC Megi, the westerly anomalies will strengthen with altitude, which will lead to the southward movement of ridge increasing with altitude, too. In addition, the diagnostic analysis results of temperature tendency equation show that the horizontal advection anomalies and non-adiabatic heating anomalies caused by TC Megi mainly lead to the abnormal increase of atmospheric temperature, while the vertical transport anomalies are always beneficial to the abnormal decrease of atmospheric temperature. It is concluded that thermal effect of TC plays an important role in the process of changing the vertical distribution of WPSH ridge lines.