Abstract: Macroalgal blooms are increasing globally as a result of anthropogenic stressors and climate change. Globally, green macroalgae were found to be the most reported and spatially distributed blooming algae leading to negative environmental and socio-economic impacts. The massive green tides caused by Ulva prolifera recurrently in the Yellow Sea for 17 consecutive years by 2024 have been recognised as the largest scale in the world. The prevention and mitigation of Yellow Sea green tides has become an important part of China’s coastal ecological safety. In this paper, the main types, geographical distribution and ecological consequences of macroalgal blooms in the world were reviewed. Then, the origin, formation mechanism and the key driving factors on the outbreak and maintenance of Yellow Sea green tide were thoroughly analyzed. The Yellow Sea Ulva prolifera green tide is originated from the Subei Shoal has reached a scientific consensus. The green algae attached on the aquaculture rafts were identified to be the only biomass source of early stage floating macroalgae. The development of Yellow Sea green tide is influenced by multiple environmental factors and hydrodynamic field combined with human interventions and climate change. Specifically, Porphrra yezoensis culture activities primarily affect the source biomass, seawater temperature and nutrient level mainly affect the growth and diminishment of Ulva prolifera, monsoon and the wind-driven surface currents determine the drifting path and retention time of the floating algae during different stages. Overall, climate change will cause significant annual flucutaitons of green tides in terms of our break time and scale, drifting path and time of duration through the modulations of meterological and circulation conditions.