Chlorophyll-a (Chl-a) concentration serves as a crucial indicator of marine phytoplankton biomass, reflecting the richness and diversity of marine ecosystems. Satellite remote sensing technology offers significant advantages in monitoring the spatiotemporal distribution of large-scale Chl-a concentrations across global ocean waters. Using MODIS （Moderate Resolution Imaging Spectroradiometer） Chl-a concentration data from 2003 to 2022, this study analyzes the spatiotemporal variability and trends of the Chl-a concentrations in global oceans, and their relationships with the global sea surface temperature (SST), El Nio-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) are examined. The results are outlined below. (1) Spatially, the Chl-a concentrations in coastal waters are generally higher than those in offshore waters, with the lowest concentrations observed in pelagic waters (less than 0.03 mg·m-3). Seasonally, Chl-a concentrations exhibit significant variations, with nearshore waters showing more pronounced seasonal changes than pelagic waters. (2) In the open waters of the Pacific, Indian and Atlantic oceans, the trend of the Chl-a concentrations remains mildly changes. However, Chl-a concentrations show an increasing trend in the majority of nearshore waters. (3) The months with the highest Chl-a concentrations across global ocean waters vary in a band-like pattern with latitude. (4) Generally, the Chl-a concentrations exhibit significant negative correlations with SST (p＜0.05) between 40°S and 40°N, while positive correlations are observed in other latitudes. The correlations between Chl-a concentrations and ENSO/IOD also display significant seasonal variations, indicating that ENSO and IOD have different impacts on the variations of Chl-a concentrations in different sea regions.