Abstract: In this article,the author analyzed a rsenic and selenium for drinking water at Xi'an peripheral locality 11 sampling point and found that the a rsenic content in drinking water is lower in south(the Qinling area)and east of Xi'an.In Hu county a rea west of Xi'an a rsenic content in drinking water is higher than other area sobviously and has achieved 0.047mg/L,approaching the mild pollution standard.The generalized analysis shows that the reason which causes this local high arsenic concentrates relatively is not single,but a combined result of natural factors and the human factors.Hu county area is situated at the Qinling orogenic zone,north of shangdan fault zone.Magmatic intrusive rock and golden ore deposit are possibly the main mother substance sources for the high a rsenic environment.Magmatic intrusive mass in Zhen'an area lying south of Shangdan fault zone is the same as Hu county,so the arsenic contentin the rock stratumis higher relatively.However,the arsenic contentin the Qinling a read rinking water is normal;furthermore,the golden ore zone is one of the factors that affects a rsenic contentin drinking water of the Hu county area.