Abstract: The STC (seasonal transition of convection) in the Maritime Continent (MC) during the boreal spring is closely linked with the onset and advance of the Asian summer monsoon. The interannual variation and impact factors of the STC are still poorly understood. This study employed the climatic characteristics of seasonal transition in the MC to define the indices of convection activity and circulation, which are the key points in the process of seasonal transition. These indices were used to analyze the interannual variation in the STC in the MC and to explore the possible effects of SSTA (sea surface temperature anomalies) in the tropics. The results revealed that the interannual variations in the STC in the MC and the evolution of atmospheric circulation over the surrounding areas are synchronous. These variations are mainly regulated by the El Niño‒South Oscillation (ENSO). Besides, the SSTA in the eastern tropical Indian Ocean, independent of ENSO, possibly stimulates anomalous local atmospheric circulation, leading to convective anomalies in the MC to a certain extent.