With the development of the observation system, our understanding of the Indian Ocean circulation has advanced in recent years. We have noticed the rapid increase in ocean heat content in the Indian Ocean and its role in global climate change. In the mean state, a single current loop is established by an eastward current along the equator and a westward current south of the equator, regarded as the Indian Ocean Tropical Gyre (IOTG). As an important component of Indian Ocean air-sea interaction, the IOTG plays an essential role in modifying upwelling systems off the Java-Sumatra and Somalia coasts, as well as in the southwest tropical basin. Due to the monsoon, IOTG displays significant seasonal variations, characterized by the reversal of currents and associated heat-salt redistribution. IOTG interacts with the climate modes. The Indian Ocean basin mode reduces upwelling off the Somali coast and in the southwest tropical basin during spring and summer, which is unfavorable to the IOTG’s seasonal northward shift. In comparison, the development of the positive Indian Ocean dipole weakens the IOTG in the autumn, in which the enhanced westward current is associated with chlorophyll blooms off the Java-Sumatra coast. This paper summarizes the advances, including the multiscale variations of IOTG, associated heat-salt transport, and its ecological impact.