The Ordovician was a crucial period for the evolution of life and the environment on Earth. During this period, there was a remarkable radiation of life known as the Great Ordovician Biodiversification Event, and the Earth""s climate shifted from a greenhouse in the Early Ordovician to an icehouse in the Late Ordovician. The Lower Ordovician Xialingnangou section in the Helan Mountains, western margin of the Ordos Basin, has excellent exposures of the Furongian to Middle Ordovician. The conodont biostratigraphy of Xialingnangou section provides valuable time constraints on the cyclostratigraphy. In this study, Ca, Fe, and Fe/Ca series were selected as palaeoclimate proxies to carry out cyclostratigraphical analyses on the Xialingnangou section. A continuous and high-resolution astronomical time scale of ~8.9 Myr was established based on the stable 405-kyr long eccentricity cycle, and the duration of the Tremadocian Stage was calculated to be 6.9 ± 0.28 Myr. The evolution spectra of the ratio of obliquity power and short eccentricity power to total power reveal a super-long obliquity cycle of ~1.2 Myr (s4–s3) and a super-long eccentricity cycle of ~2.4 Myr (g4–g3) in the Early Ordovician. Meanwhile, the sedimentary noise models of the tuned Ca, Fe, and Fe/Ca time series show high-resolution sedimentary noise fluctuations corresponding to sea-level changes. This reveals that sea-level changes were mainly driven by the super-long eccentricity cycle (s4–s3) in the early Tremadocian Stage, whereas in the middle Tremadocian to early Floian, they were mainly controlled by the super-long eccentricity cycle (g4–g3). The adjustment of the astronomical periods in the Early Ordovician may have played an important role in promoting the Great Ordovician Biodiversification Event.