The risk assessment of flood disaster is the basis for the scientific decision of disaster reduction. Based on the risk assessment model of flood,the paper aimed at the characteristics of flood disaster in protected area to choose the largest submerged depth,the maximum velocity of flood，flooded duration，GDP and population as evaluation index.Than it used the variable fuzzy comprehensive evaluation method to build the risk assessment model of regional flood disaster which is suitable to the protection area.It took the risk assessment in different scenarios of flood disaster at downstream of protected area of Hebei L River for example,and investigated to build and apply the model.The result shows that the physical significance of the improved model is clear，calculation is simple and with high reliability.The result can provide basis for the management of flood disaster.