When the Nash Unit Line method is used to calculate the flood peak in a project，the maximum value of the flood peak is taken as the flood peak from the limited calculation node，and there is a certain error.When higher accuracy is required，it is not appropriate to count only the maximum flood value at the limited calculation node as the design flood peak.The blind mountain-climbing method and the semi-divided method are excellent methods for calculating flood peak flow，which are simple and clear，have limited calculation overhead and fast convergence speed，and can be used by many design colleagues for reference.