///In order to provide reliable and exact and detailed design for railroading in Lop Nur area, the authors analyzed engineering geological condition and hydrogeological condition based on the result of reconnaissance and experimentation. Directed at the characterization that the content of Na₂SO₄ and Nacl are higher during the surface of saline rock in Luo-bupo area, analyzed the engineering physics and mechanical properties that change the saline rock as subgrade, made suggestion about subgrade construction, based on the practice and theoretical analysis of the saline region, proposed a convenient and practical method to judge and calculate the content salinity of the fragmentized rock.