The Shamuluo Formation is distributed in Bangong Co-Nujiang suture zone, and its sedimentary background and source characteristic were closely linked with the evolution of Bangong Co-Nujiang Tethys Ocean. In order to discuss sediment provenance, weathering, tectonic setting of sedimentary basin and subduction of Bangong Co-Nujiang Tethys Ocean, the authors made a systematic analysis of petrology and geochemistry of Shamuluo Formation argillaceous rocks in the western part of the Bangong Co-Nujiang suture zone. The mean values of ICV, CIA, Al₂O₃/TiO₂, Th/Sc, Rb/Cs, (Gd/Yb)_N, La, Ce, ∑REE, La/Yb, (La/Yb)_N, Eu/Eu_N^*, LREE/HREE are 0.80, 72, 21, 0.88, 13.5, 1.58, 42.47×10^-6, 84.81×10^-6, 200.02×10^-6, 14.22, 9.61, 0.65 and 9.04 respectively, while the mean values of Th, U, Hf, Th/U, La/Th are 16.34×10^-6, 2.85×10^-6, 4.81×10^-6, 5.78 and 2.61 respectively. The diagrams of K₂O/Na₂O-SiO₂, La-Th-Sc, Th-Co-Zr/10, Th-Sc-Zr/10, TiO₂-Zr, Co/Y-Ti/Zr, La-Th-Sc, Th-Sc, La/Sc-Co/Th, REE-La/Yb, A-CN-K and REEs also show certain regularity. The argillaceous rocks are mature and the source rock are granodiorite, granite, andesite and sedimentary clastic rock which have much plagioclase and alkali feldspar. The source region of argillaceous rocks has suffered from medium degree of chemical weathering, suggesting a warm and moist climate. The geochemical characteristics of argillaceous rocks indicate that argillaceous rocks tended to occur in active continental margin setting, where its tectonic activity became intensified from the bottom to the top. These results provide sedimentary geochemical evidence for the evolution of Bangong Co-Nujiang Tethys Ocean, which indicates that Bangong Co-Nujiang Tethys Ocean experienced northward subduction about 141 million years ago.