The ERA-Interim reanalysis dataset is used to investigate the climatological characteristics of the South Asia High (SAH) formation and related possible mechanisms. In addition, we examine the influence of ENSO events on the interannual variability of SAH formation. The results indicate that the climate-mean SAH is generated in the upper troposphere over the southeastern Indo-China Peninsula on the 24th pentad. The process is attributed to enhanced convection over the southern Philippines and the Indo-China Peninsula in late spring. Convection over the southern Philippines is intensified to produce a negative vorticity source to the north, which is transported to the South China Sea (SCS) by the tropical upper easterly to induce a close anticyclone in the upper troposphere, representing the preliminary generation of SAH. Furthermore, convection over the Indo-China Peninsula facilitates the development of SAH, moving its center to the upper troposphere over the peninsula. The meridional position of convection near the Philippines determines the formation location of SAH, whereas the enhancement and northward migration of SAH is controlled by the strength of convection over the Indo-China Peninsula in late spring and early summer. Therefore, the warm and cold phases of ENSO events could influence the pattern and position of SAH during its formation process via regulation of the convection over the two regions. After the occurrence of warm ENSO events, tropical convection is intensified to the east of Kalimantan, resulting in SAH establishment in the upper troposphere over northern Sumatra and the Gulf of Thailand. Meanwhile, the convection over the Indo-China Peninsula is too weak to support the northward movement of SAH. Conversely, cold ENSO events contribute to reinforced convection over the mid Philippines, stimulating SAH over the central Indo-China Peninsula. Subsequently the rapid flourishing of convection over the Indo-China Peninsula cases SAH to expand westward and shift significantly northward. Thus, the warm and cold phases of ENSO events have significant effects on the formation location of SAH.