Abstract: According to the result of characteristic of peak flow, this paper has proved that the peak flow has the random and fractal characteristics. The index of Hurst displayed the obvious trend of the series of flood in Wujiang River. And the flood has characteristics of durability and long-term memory. V value show that the ascend trend of peak flow will disappear after six years. Durability of 53 floods are obviously increase on WuJiang River. The results show that, the change of flood time sequence have been important influenced by human activities ,typhoon and drastically changed climate.