Abstract: As a key tectonic unit in the southwestern margin of the Central Asian Orogenic Belt（CAOB）, the West Junggar region is critical for clarifying the provenance system and tectonic setting of the Late Paleozoic Kujiertai Formation. In this study, clastic rocks of the Kujiertai Formation were selected as the research object, and systematic LA-ICP-MS detrital zircon U-Pb dating and trace element analysis were carried out. A high-precision detrital zircon age spectrum and a supporting geochemical database of the formation were established. Combined with the method for reconstructing crustal thickness using zircon Eu anomalies, these data provide important constraints for revealing the provenance characteristics and tectonic evolution background. The results show that the Th/U ratios of detrital zircons from the Kujiertai Formation range from 0.81 to 4.03 (all greater than 0.4), indicating a typical magmatic origin. The zircon U-Pb age spectrum shows that the main ages are concentrated in the range of 510–290 Ma, with five distinct peak intervals: 430–390 Ma, 380–365 Ma, 365–340 Ma, 340–320 Ma and 320–290 Ma. Among them, the youngest zircon age is 298 Ma, which provides key chronological constraints on the sedimentary age of this stratigraphic sequence, suggesting that the sedimentation occurred no earlier than the Early Permian. Geochemical characteristics reveal that the provenance is dominated by acid granite (accounting for approximately 68%) and mafic basalt (accounting for approximately 30%), reflecting prominent magmatic rock features in the provenance area. Integrating with the regional geological background, this study holds that the provenance system of the Kujiertai Formation is mainly controlled by the multi-stage tectono-magmatic activities of the Boshkul-Junggar Magmatic Arc, the Zarma-Sawuer Magmatic Arc and the Darbut Ophiolite Belt. Through systematic analysis of zircon Eu anomaly characteristics and combined with the timing of regional magmatic activities, the Paleozoic crustal thickness variation sequence of the study area was reconstructed. This result provides independent geochemical evidence for clarifying the complex tectonic evolution process of "accretion-transformation-disturbance adjustment" experienced by the West Junggar region during the Paleozoic Era.