The economical risk analysis in urban flood control engineering is very important for planning and evaluating schemes of urban flood control engineering. In this paper, Monte-Carlo method for economical risk analysis in urban flood control engineering is discussed, and the key of the method is how to establish the random simulation model by which uniformly distributed random number series can be transformed into the studied economic index series. The result of examples analysis shows that Monte-Carlo method can consider more things than analytical methods, the computation result of Monte-Carlo method is more nicety, and the simplified analytical methods should be used carefully in economical risk analysis of important city flood control engineering becauses their computation less precision.