Abstract: As important marginal seas of western North Pacific Ocean, the East China Seas (ECS, including the Yellow Sea and Bohai Sea, here) and the South China Sea (SCS) has been subject to the impacts of global climate change in terms of primary production and fishery production. Thus, it is important to analyze and review the phytoplankton response to global climate change. This paper uses the reconstructed remote sensing data and references to analyze and review the interannual and interdecadal effects of Sea Surface Temperature (SST) and some other factors such as wind field on chl-a, primary production, abundance and biomass. This paper also analyze phytoplankton community structures in recent decades, and discusses the causes of dominance of nanophytoplankton and picophytoplankton and dinoflagellates, and the appearance of warm water phytoplankton species in offshore China seas and adjacent sea areas. The result shows that phytoplankton community structure and biomass has changed significantly with dominating picophytoplankton and dinoflagellates and northward distribution of warm water species. In addition, the chl-a biomass increase (decrease) slightly in the ECS (the SCS) and it shows much complicated relations with SST warming though there may have shown positive (negative) correlations. We also find that SST warming has less effects on chl-a and primary productivity in the ECS compared with the SCS because of interactions of East Asia monsoon, near shore circulation and the supply of terrigenous nutrients to the sea. Picophytoplankton and dinoflagellates trend to dominate in poor nutrient waters due to SST warming and nutrient structure variation, which becomes complicated due to overlapping effects of environment factors. At last, imperative studies are proposed for the impact of global climate change on the marine ecosystem of the offshore China seas and adjacent sea areas.