We present a new multiproxy dataset of grain size, Mg isotopes and major elemental compositions of sediments from the International Ocean Discovery Program Site U1483, situated in the northwestern Australian margin, in order to reconstruct the terrestrial sediment supply to the southwestern Timor Sea, as well as the continental weathering and erosion history in the source region since 200 ka. A second objective is to explore the potential of δ 26Mg values of fine- grained siliciclastic marine sediments in tracing paleoclimate changes. The results demonstrate that terrestrial siliciclastic fraction of sediments at IODP Site U1483 are mainly composed of clay silt, with δ 26Mg values ranging larger than 0. 25‰. The Chemical index of alteration (CIA) and two physical erosion parameters including mass accumulation rates (MAR) and Ti/Ca ratios are reported. Over the last 200 ka, the δ 26Mg index shows a shape of curve in a great similarity with that of the CIA, suggesting that Mg isotope compositions are mostly indicative of weathering intensity changes in the source region, and are little influenced by mineralogical sorting, lithology and early diagenesis. Combined with regional paleoclimate records, we notice that our new weathering and erosion data show nearly synchronous co- variations with published Australian summer monsoonal precipitation and the sea surface temperature records from the same site since 200 ka. However, there is relatively low coherence between our data and the sea level in the equatorial Pacific. By compiling the data, this study suggests that the weathering and erosion evolution of the source region on the orbital timescale were mainly controlled by the Australian paleo- monsoon system during the last 200 ka, pointing to the “climate- driving weathering” pattern. The application of δ 26Mg index provides a new isotopic perspective on understanding regional continental weathering and its response as well as feedback mechanisms to the climate evolution.