Using the reanalysis data derived from numerical model and the routine observation data, the mutual influence and interaction between the significant circulation systems in the westerlies, subtropics and tropical area during the summer of 2009 were studied by composite and correlation analysis. The complete form of vertical vorticity tendency equation was used to explore the dynamic mechanism for the northward jump and strength maintenance of the subtropical high. The study reveals that the variance of the subtropical high is closely related to the propagation of the westerly wave, and the jump of the west Pacific subtropical high starts at the strengthening of the middle part of subtropical high (140°-160°E); Severe convection over the Bay of Bengal occurred previous to the northward jump of the subtropical high, which has indicative significance to the forecast of the jump and strengthening of the subtropical high. Nevertheless, the convective activities south to the subtropical high have accompanying relationships with the northward jump of subtropical high; meanwhile, from the perspective of dynamic mechanism, the key factor of northward jump of the subtropical high is the variance of the vorticity over East Asia coastal areas, which is caused mainly by the movement of the trough and ridge in middle high latitudes.