<p>The Madden–Julian oscillation (MJO), as the most significant tropical intraseasonal phenomenon, affects the global weather and climate. The impacts of different oceanic processes on the development of atmospheric convection during the eastward propagation of MJO have been emphasized in the previous studies. The MJO simulations in the Regional Coupled Ocean–Atmosphere–Wave–Sediment Transport (COAWST) model are compared with the Climate Forecast System Reanalysis (CFSR) daily reanalysis data, and the critical path of MJO propagation across the Maritime Continent (MC) is identified. Similar to the results of the previous studies, the air–sea coupling and the oceanic transport processes contribute significantly to the eastward propagation of MJO in the coupled simulations. The enhanced sea surface upward heat- and vapor-fluxes resulted from the warmer surface ocean cause positive anomalies of the moist static energy (MSE) in the lower atmosphere, promoting the development of the atmospheric convection. Further detailed analysis based on the sensitivity experiments highlights the key role of the topographic-related temperature transport and vertical heat diffusion processes within the MC to the maintenance of warm SST prior to the MJO. The study proposes a new mechanism of the oceanic impacts on the MJO propagation in the MC, deepening the understanding of the relevant processes and providing a novel perspective for the optimization of MJO forecasting.</p>