Abstract: in order to understand the Jurassic underground water system afected to the mining of the Jurassic Coalife , it was necessary fom the basin dimensionto study the features of Jurassic underground water system in Ordos Basin. With a comprehensive anaysis and stidly conducted on the hydrodiynamic fe d, hydrochemical feld and isctope fied of the Jurassic underground water in Ordos Basin,the paper pointed out tht the Jurassic underground water systen manly had to fowing modes of a gravity fiow and a compaction f1ow.Among the two fuids ,the topline of th Jurassic mainly with the compaction fov had a deeper depth over 1 200 m than Tanhuan Depression and other sections were mainly the gravity fow.The stutly showed that the Jurassic underground water system of Oros Basin could be didedto wo water-bearing subsystems and six sub-systens in an exposed zone and concealed zone. The mine water infow volume fron the shall w atenative actve zone witha depth of