The NCEP/NCAR reanalysis data are mostly used to investigate the variability of South Asian high(SAH) and its relation to sea surface temperature(SST) in previous studies,but the results from these studies have one-sidedness.Thus,this paper compares the summer SAH intensity variation and its relation to SSTs using five reanalysis data (ERA-40,ERA-Interim,NCEP/NCAR,NCEP-DOE and JRA-25) and three simulation results from which the atmospheric general circulation model NCAR CAM5.1 is driven by the observed monthly global,tropical Indian Ocean and tropical Atlantic Ocean SSTs during 1978—2008,respectively.Comparisons in SAH intensity among these reanalyses show that there is a very distinct difference in SAH intensity variation between the two reanalyses(NCEP/NCAR and NCEP-DOE) and the other three reanalyses(ERA-40,ERA-Interim and JRA-25) during the period of the late 1970s to the early 1990s,indicating that the abrupt increase of SAH intensity in NCEP/NCAR and NCEP-DOE reanalyses maybe not true during this period.The possible false data lead to a distinct difference in relation of SAH intensity to SST anomaly between the former two reanalyses and the latter three.Results from the three reanalyses(ERA-40,ERA-Interim and JRA-25) and three experiments show that summer SAH intensity anomaly is closely associated with the tropical Indian Ocean SST anomaly in previous winter,previous spring and contemporaneous summer after 1970s,indicating that the tropical Indian Ocean is a key area to affect the summer SAH intensity.When the tropical Indian Ocean is warmer than the normal,the tropospheric temperature will be warmer in tropics,in such a way that SAH intensity will be enhanced,SAH area enlarged,and SAH location extended southward,eastward and westward,and vice visa.