Under the pressure of global changes and human activities, the structure and function of marine ecosystem changed significantly. The ecological disasters including red tide, green tide and white tide (jellyfish blooms) occurred frequently. As representatives of the gelatinous plankton, the increasing of jellyfish abundance caused much controversy and interpretation internationally: the outbreak of jellyfish is a trend or a cyclical phenomenon. The key question is the understanding of the cause of jellyfish bloom. To solve these problems, a comprehensive investigation was carried out on the basis of Major State Basic Research Development Program entitled "Key processes, mechanism and ecological conse- quences of jellyfish bloom in China coastal waters". The research progress of the project will be published in this special issue. This progress is related to the jellyfish life history strategies, the impact of environmental factors on the growth and development of the different life history stages of jellyfish, the impact of jellyfish bloom on environment, as well as the new perception on the mechanism of jellyfish bloom in China coastal waters.