With gradual completion of surrounding mine in Ordos Basin, the overlying thick aquifer continued to enter mine along with large amount of coal mining. A number of mine water disasters occurred due to inadequate design of drainage ability, especially mine water inflow quantity in exploration stage was predicted by steady flow pumping test but ignored release of static reserves. Taking surrounding Nalin River No.2 Well as an example and making full use of hydrogeological parameters obtained from stages of pumping test in exploration stage, as well as considering prediction of mine water inflow by static reserves, mechanism of mine water gushing under thick aquifer was characterized and compared with mine water inflow in recent years, error rate was predicted, accuracy of predicted results was improved, which provided a reference for prediction of mine water inflow quantity in the region.