Abstract: Based on analyzing the trend of Hurst exponent and considering the length of time series, as well as the relation among inflow water data in mines, a quantitative prediction of R/S method from qualitative to quantitative of nonlinear time series has been obtained by computer successfully. Taking the inflow water in Zhaojiazhai Mine as the example, the time series of inflow water, before and after water inrush, have been carried out by the quantitative prediction of R/S method. The prediction accuracy is as high as 92.48% and 94.75% respectively. It shows that the model has high-precision and strong applicability.