The Asian summer monsoon is a complex phenomenon and two distinct stages of poleward movement of the summer monsoon rainbands are found over Southeast Asia and India. The Asian summer monsoon is often divided into two major systems: the Indian monsoon system and the Southeast and East Asian monsoon system. An idealized monsoon study shows that the land-sea contrast creates a monsoon rainband along the southeast region of the continent and continues on to the neighboring ocean. This rainband moves northward as the sun propagates northward. In Asia, besides the original land-sea contrast, the Tibetan Plateau creates another heating contrast to the surrounding continental areas. The Southeast Asian monsoon system is created by the Asian continent and the surrounding oceans. The Indian monsoon system is due to the contrast of the Tibetan Plateau and the surrounding lands. The Asian summer monsoon, therefore, can be treated as an overlapping of two heating contrasts which can create two distinct rainband movements. An intermediate atmospheric model coupling with a simple land surface and a mixed-layer ocean is used to examine this new aspect and the detail will be discussed.