The frost-heaving and thawing-settlement of roadbed are often met in Qinghai-Tibet Railway, especially in salty soil area. Thermal characteristics of salty soil are researched by TG-DSC technique. The results show that soluble salts have great influence on thermal characteristics of salty soil; water content gets higher, phenomena gets acuter. Freezing force depends on water content and freezing temperature; the more water content or the less temperature is, the more intensive of freezing force is. The conclusion has guiding significance for mastering the characteristics of frost heaving and thawing-settlement in salty soil area of Qinghai-Tibet Railway.