Based on the annual average NCEP/NCAR reanalysis data,the seasonal variation characteristics of the intensity and location of the Middle East jet stream(MEJS) and their relations with the SouthNorth temperature differences(SNTD) are discovered.Results show that there are obvious seasonal variation characteristics for the vertical structures of intensity and location of westerlies over the Middle East area.The intensity of westerly center is stronger in winter and spring,but weaker in summer and autumn.Above 600 hPa,the location of westerly center is southward in winter and spring,but northward in summer and autumn.In each season,the velocity of 200 hPa westerly center is maximum.The intensity and location of MEJS have obvious seasonal variation characteristics.MEJS is stronger and locates in 275°N from November to the next April.MEJS is weaker from May to October and moves northward after May with its center maintaining over about 40°N from June to September and 325°N in October.The seasonal variation characteristics of the intensity and location of MEJS are significant with good corresponding relations to the SNTD averaged from 500 to 200 hPa.It shows that the seasonal adjustment of SNTD has important effects on the seasonal variations of intensity and location of MEJS according to the principle of thermal wind.