Abstract: To simulate the sandstone ore leaching process, some specimens with different grades were made with river sand, cement and salt as the raw materials. On the basis of the monitoring of leaching solution concentration in a water-solution mining experiment, the time evolution of leaching solution concentration and leaching rate was examined. Through phase space reconstruction from the time series of leaching solution concentration, the distance evolution of points of specimens with different grades in the phase space was revealed by the chaotic theory. A prediction model of the distance evolution of phase points was established by using the grey theory, and a reasonable leaching period was ascertained. The results show that the leaching solution concentration holds chaotic characteristics. After the phase space reconstruction, the delicate changes of leaching solution concentration are enlarged, and the internal rules are fully demonstrated. The ores of different grades have different nonlinear dynamic behaviors. Based on the phase space reconstruction, the leaching period has been predicted by means of the residual modification grey model, which provides a new research method and theory to solution mining.