The East China Sea (ECS) is threatened by frequent Skeletonema costatum (S. costatum) blooms every year, which can cause severe environmental harm, as well as considerable economic losses. Remote sensing is an efficient tool for monitoring these harmful algal blooms (HABs) and studying concerned marine conditions. This study investigated two intensive S. costatum HABs in the ECS by analysis of water distribution and spatial-temporal pattern of four oceanographic parameters derived from moderate resolution imaging spectroradiometer (MODIS) and QuickSCAT satellite data using multiple remote sensing approaches (composite imagery interpretation, classification, and parameters retrieval). Results show that high chlorophyll-a (Chl-a) concentrations and net primary production (NPP) decrease from the HAB areas toward the open sea. A peak of Chl-a () and NPP () are considered indicators of large-scale S. costatum blooms in the ECS. Low sea surface temperature (SST; approximately 23°C) are observed in S. costatum HAB areas. In early stages, winds in terms of direction and speed can bring nutrients to facilitate the formation of S. costatum blooms, but then sharply change into unfavorable conditions to cause the final disappearance of HABs. This study also explored multiple oceanographic explanations in the ECS from biochemical, meteorological, physical, and geological perspectives for a better understanding of such S. costatum HABs mechanisms.