Abstract: Watershed over-standard flood has always been an important issue plaguing the world, which can lead to devastating impacts on social and economic development. How to identify the new characteristics and risk factors of watershed over-standard flood disasters under changing environment is a major scientific problem that governments and hydraulic workers in various countries urgently need to study and solve. Taking the Changjiang River Basin as an example, from the four dimensions of climate change, change of watershed underlying surface, construction of flood control system, and economic and social development, we dynamically reviewed the new characteristics of watershed over-standard flood disaster and risk caused by environmental changes. The results show that global climate change has increased the probability of over-standard floods, and the periodic changes of large floods also indicate that there is a higher possibility of over-standard floods in the future. Soil and water conservation measures have reduced the threat of over-standard floods. The status of the ‘flood overbank - home reconstruction -re-overbank flooding’ vicious cycle in the bottomland has not fundamentally changed. The contradiction between flood storage and development protection has increased the risk of operation and utilization of over-standard floods in the Changjiang River Basin. The improvement of the Changjiang River Basin flood control system has increased the defense against major floods. However, due to the difficulties of flood diversion in the flood storage and detention areas, difficulties in ensuring discharge capacity in river channels, and the contradictions that cannot be effectively coordinated between external flooding and internal waterlogging, it is still unable to fully controlled the over-standard floods in the basin. Economic and social development, especially the effect of urbanization and agglomeration, has led to a sharp increase in the risk of over-standard flood and a change in the pattern of flood control risk, so every region has become more and more overwhelmed. People ’s longing for a better life has increased the expectations of reservoir overstorage and flood discharge in the river channels, intensified the difficulty in coordinating flood control scheduling decisions. The research results have important scientific value and strategic significance for the scientific defense of the over-standard floods in the Changjiang River Basin.