From the COADS (Comprehensive Ocean–Atmosphere Data Set) I and the COADS II, we got a monthly data set of sea surface temperature (SST), zonal and meridional wind components at sea level (U,V) and sea level pressure (SLP) with 4° × 4° grid system covering the period from Jan. 1950 to Dec. 1987 to study the evolutional features of the quasi-biennial oscillation (QBO) in the air-sea system. The analytic method of complex empirical orthogonal function (CEOF) is used to obtain the composite temporal sequences of amplitude (six phases for half a period) for the first and the second main components of SST, U, V and SLP. It is shown from the results that the main characteristics for different phases of the sea surface temperature anomaly’s (SSTA) QBO are warm water / cold water in the equator of the eastern Pacific (EEP). There are two warm or cold water centers of the SSTA in the EEP, which are located in the equator of the central Pacific (ECP) and the east part of the EEP. The features of the source propagation and the influence of these two centers on atmospheric circulation are discussed and it can be seen that in the formation of these two centers, there are different features in oceanic and atmospheric circulations and air-sea coupled process.