The concepts, including flood risk, risk analysis, risk management, as well risk governance, were discussed in this paper. It pointed out: (1) The idea of flood disaster reduction was changed from “flood control” in the early 20 century, to “flood-induced loss reduction” in the late 20 century, then to “flood risk reduction” in the 21 century, and the changes were closely related to the practical situation of flood disaster reduction, social public administration level, etc, in different stage. (2) Risk in flood disaster reduction was sourced from uncertainties in spatial and temporal distribution of flood, receptors of disaster, and measures of disaster prevention and reduction, etc, therefore, flood risk analysis should be based on practical situation of flood aiming at different issues. (3) Risk governance in flood disaster reduction emphasizes public involvement mechanism, and tries to provide a satisfied decision based on comprehensive evaluation for risk of profit and loss for each stakeholder according to multiple uncertainties in different evolution stages of flood disaster. Finally, this paper emphasized the importance of human factors and its uncertainties in the practice of risk management for flood disaster reduction.