The NCEP/NCAR and ECMWF reanalysis data were used to analyze the difference of zonally mean meridional wind and mass stream functions between the two data sets from 1979 to 1989.The result shows that the Hadley cell in the ECMWF data had an obvious bi-level structure,but there was no such phenomena in the NCEP/NCAR data.Although this paper cannot verify whether Hadley cell actually has a bi-level structure or not,it does clarify that the choice of data has direct effect on the research result of the low-latitude general circulation.