Tracing pedogenic processes is fundamental for reconstructing climatic and environmental changes using loess deposits. Lithium isotopes can serve as a sensitive tracer to unravel these processes, owing to its active behaviors without effect by redox and biological reactions. This study investigated the Li contents and delta Li-7 values of leachate and residue ([Li](leachate), [Li](residue), delta Li-7(leachate) and delta Li-7(residue)) of the upper 12.5m Luochuan loess-paleosol sediment (since the last interglacial) on the Chinese Loess Plateau, in order to better understand pedogenic processes in loess. The [Li](leachate), varying from 0.39 to 1.97 mu g/g, is mainly derived from the adsorption phase, with a significant variation in delta Li-7(leachate), from -6.55 parts per thousand to +12.88 parts per thousand. Both [Li](leachate) and delta Li-7(leachate) variations reflect weathering and adsorption processes during different periods. The [Li](residue) vary from 34.4 to 46.3 mu g/g (averaging 38.4 mu g/g) and their delta Li-7(residue) vary from -3.66 parts per thousand to +2.44 parts per thousand (averaging -0.22 +/- 1.68 parts per thousand), both in agreement with the upper continental crust values. At initial stage after loess deposited (stage I), high [Li](leachate) but low delta Li-7(leachate) are results of preferential adsorption of Li-6 by clays and migration of 7Li with soil solution during weathering and eluviation processes. When overlying loess was deposited and experienced pedogenesis as the stage I, Li-7 migrated downward and was adsorbed by clays (stage II), resulting in high [Li](leachate) and delta Li-7(leachate) in underlying loess. When loess has superimposed pedogenic and adsorption processes as the stages I and II, loess became as paleosol with highest delta Li-7(leachate) in underlying carbonate accumulation layer. A persistent increase in delta Li-7(leachate) indicates dominant control of post-depositional adsorptions on Li fractionation along solution migrations during weathering and eluviation of overlying deposits, and vice versa. These results highlight that variations in [Li](leachate) and delta Li-7(leachate) can be used to trace soil water migration processes and the magnitude of pedogenic processes in loess-paleosol sediment at different periods. (C) 2021 Elsevier Ltd. All rights reserved.