Abstract: Characteristics of the Northern Hemisphere sub-tropical high seasonal splitting from spring to summer and its possible mechanisms have been analyzed on the basis of climatological data sets. Results suggest that the splitting of the sub-tropical high occurs over the Bay of Bengal to the Indo-China peninsula. However, since March to May, remarkable contrast exists in the meridional cell at the lower and upper level over these sectors, where the land surface sensitive/latent heating fluxes both play an important role and cause the local Hadley cell over the Indo-China peninsula to exhibit an enhanced vertical upwelling in behavior, in contrast to the dominant land surface sensitive heating flux which causes the vertical, local reversed Hadley cell over the Bay of Bengal. Thus, the vertical splitting of sub-tropical high in unity should be over the Indo-China peninsula, rather than the Bay of Bengal at lower levels. In addition, the analysis also suggests that the faster seasonal land snow melting in the east of Indo-China peninsula can enhance the quickly increasing land surface sensitive heating of atmosphere and weaken the local Hadley cell in these sectors, which supplies a favorable climate background for the splitting of Northern Hemisphere sub-tropical high.