A scheme is proposed for calculating the stream function of the mass in meanmeridional circulation in the GCM of low resolution vertically. Results show that for the model Hadley circulation,its seasonal change is identical to that of the real atmosphere.It isfound that,separated from the mean meridional circulation of the model atmosphere in the El Niño year can be an anomalous circulation in close relation to the El Niño-type SST anomaly,which gives rise to the lagging transition of the average Hadley circulation into the northernmid summer type.