根据一定洪涝指标建立了长江下游地区近五百年洪涝序列，对该序列的Ｈｕｒｓｔ指数的计算以及滑动序列和滑动定长序列Ｈｕｒｓｔ指数谱的分析，表明：长江下游地区洪涝序列是分数布朗噪声序列，具有较明显的Ｈｕｒｓｔ效应；其Ｈｕｒｓｔ指数Ｈ及Ｈ指数谱离Ｈ＝１／２的白噪声序列较近，具有较强的随机性和较弱的持续性。Ｒ／Ｓ分析要求较长的序列长度，长江下游地区洪涝序列稳定的序列长度在４００个样本量以上 Based on a certain flood index, a series of flood sequences in the lower reaches of the Yangtze River have been established. The calculation of the Hurst index and the Hurst exponent of the sliding sequence and the sliding length sequence shows that the flood sequences in the lower reaches of the Yangtze River are fractional Brownian noise sequences , Which has obvious Hurst effect. The Hurst index H and H index spectrum are close to the white noise sequence with H = 1/2, which has strong randomness and weak continuity. R / S analysis requires a longer sequence length, and the sequence length of flood sequences in the lower reaches of the Yangtze River is above 400 samples