The characteristics of temporal and spatial distribution and fractions of thallium in floodplain sediments (soils) of Liaoning Province were dealt with in this paper based on the basic thought of "chemical time bombs (CTB)".Seventeen samples of floodplain sediments (soils) which covered all the area of Liaoning Province were obtained through wide-spaced sampling,and four fractions,i.e.,silicates-bound (SILB), sulfides-bound (SLJLB),organically bound (ORGB) and Water-soluble (WS) fractions, were found through fractionation.The results indicated that:1.From pre-industrialization (1943) to now (1993),the content of thallium in soils of Liaoning Province increased obviously with the rapid development of industry and agriculture,and some parts such as the Daling River Basin and Taizi River Basin have been slightly polluted by thallium,therefore,it could be predicted that the area polluted by thallium would increase fifty years later (i.e.,the year 2043).2.Thallium mainly existed in SILIB and WS fractions,secondarily in SLTLB and ORGB fractions.3.The accumulation of thallium in the soils and sediments was mainly caused by human activities,and the rate of accumulation was closely related to the fractions of thallium.4.The fractions of thallium in the soils and sediments were related to the physical and chemical properties of soils and sediments themselves such as soil types,pH and organic matter to a certain extent.