According to the theory of continuous life, the paper gave distribution flood risk assessment model of series linked hydraulic structures system in different serving periods on the condition of weibull distribution by the full use of history flood information. The model was appied in Hebei section of middle route main canal in south to north water transfer project．The paper set up the estimation model of flood risk of series linked water construction of the section in different serving periods．The results showed that flood risk of series linked water construction is closely related to not only the traditional design standard but also serving period．The paper established the evaluation model of flood risk of dynamic hydraulic structures．