Seagrass decline caused by the macroalgae blooms is becoming a common phenomenon throughout temperate and tropical regions. We summarized the incidence of macroalgae blooms throughout the world and their impact on seagrass beds by direct and indirect ways. The competition for living space and using resources is the most direct effect on seagrass beds when macro algae are blooming in an aquatic ecosystem. The consequence of macroalgae blooms ( e . g ., light reduction, hypoxia, and decomposi tion) can produce significant indirect effects on seagrass beds. Light reduction by the macroalgae can decrease the growth and re cruitment of seagrasses, and decomposition of macroalgae mats can increase the anoxic and eutrophic conditions, which can further constrict the seagrass growth. Meanwhile, the presence of seagrass shoots can provide substrate for the macroalgae blooms. Control ling nutrient sources from the land to coastal waters is a general efficient way for coastal management. Researching into the synergis tical effect of climate change and anthropognic nutrient loads on the interaction between searsasses and macroalgae can provide valuable information to decrease the negative effects of macroalgae blooms on seagrasses in eutrophic areas.