Abstract: One of the most prominent features of the intraseasonal oscillation (ISO) is its complicated propagation. To investigate the characteristics of the ISO propagation and the influences of different propagating components of the ISO, we here propose a further developed space-time spectral analysis method, the spacetime wave propagating decomposition (STWPD) based on the wave theory. The analyses using both ideal functions and reanalysis data confirm the validity and practicability of the STWPD. The result shows that any spacetime series can be decomposed into three components with different propagating directions: the progressive, retrogressive and standing waves, respectively. It is shown from the combined empirical orthogonal function (CEOF) analyses of the eastward, westward and standing components of the outgoing longwave radiation (OLR) and the zonal winds at 850 hPa and 200 hPa that: (1) the eastward component of the ISO exhibits the eastward propagation of the zonal wave number 1 and, the zonal winds at the upper and lower troposphere have a baroclinic structure and are out of phase; (2) the westward component of the ISO displays the westward propagation of the wave numbers 2-3; and (3) the standing component shows a feature of antiphase in the Indian Ocean to the Pacific Ocean. The analyses of the different components of the tropical ISO in this study may deepen our understanding of the ISO propagation and have significant meanings for constructing the physical model of the ISO and predicting it. Different from the previous methods, the STWPD provides us with a new tool and visual angle to investigate the ISO by analyzing its different propagation components. 