In this paper, four large sandy seas in North China, the Taklamakan, Kumutag, Badanjilin and Tenggeli deserts, were investrigated for geochemical Varlatlons of soluble salts in aeolian sands in order to 1) provide basic data about the concentratrons and chemistries of soluble salts in deserts of northern China; and 2) discuss the origins and causes of geographical distribution associated with the significance of atmospheric-carbon fixation in desert environnment. The studies from the Taklamakan and Badanjilin deserts suggest that variations in salt content in sedimentary sequences, interlaid by aeolian and lacustrine sediments, should be interpreted with care for palaeo-environmental changes, and combination of salt with sedimentary proxy is necessary.