Abstract: Based on the mining in the botonm group seans of 'anzhcu Coal Fied mainly hreatened by the water from Ordovician limestone in order to guide a salety mining of the bottom group seams a hydrogeologic ilig exploration.water chemcal test ock sample test.waer drainage( pumping)test.tynanic water table obseration of the aquifer and otherseveral dection means were applied to the comprehensive survey of the Ordoician limestone aquife in the medun deep secton of Yranzhou Coal Fielc. According to the information of the survey resuts,a comprehensive anaysis and study was conducted on the Orcdovician limestone auiter and the hytrogologic feature law of the Oordovicia limestone aquifer was summarzed and obtained. The stady resutis showed that the runof condititon of the Oordovican limestoneacquifer in the mediun dee section of 'anzhou Coal Field was poo and relative retention,.but the r fling was abundant and the water abundance was from weak to stong.Ca~(2+)and Mg~(2+)could be the indicated ions to distinguish the Ordovcian limestone wate:.There was a no rich water and relatveimpermeabe layer with athokness otlss than 10 m in the top of the Ordovician linestone aquifer.With the relevant water prevention and control technical measures ,a safety and prssurzed minng of the bottom group seams was feasible.