Mass stream functions(ψ) is a physical quantity describing mean meridional circulation(MMC) directly and quantitatively.Using the same grid data(1958—1998 NCEP/NCAR reanalysis data),this paper calculates ψ by using an iteration and superposition method respectively,and compares the differences and sameness of ψ in describing the MMC climatic state,anomalous MMC in the years of strong El Nino events and the double-layer structure of Hadley circulation.Results show that there is no apparent difference between them,however the superposition scheme only uses v-wind data and involves relatively simply computation.