Refering to the Xiaoqing river channel complex stochastic and undulatory property of its runoff time series，we use the wavelet transform method to analyze and explore the complex property of the runoff time series through calculating its time varying Hurst index.The results indicate that the runoff time series in the upstream of the Xiaoqing river follow a fractal distribution,with a strong persistence and long-term dependence.This provides a new idea and method for the utilization of water resources.