Objective Upward shallowing sequences are widely developed in shallow-water carbonate environments， and the identification of upward shallowing sequences in deep-water carbonate rocks has a unique advantage in analyzing the evolutionary process of shallow-water carbonate sedimentary environments. Analyzing the high-precision upward shallowing sequences of the late Cambrian Xixiangchi Formation in the Upper Yangtze region can provide important references for understanding the late Cambrian global environmental changes. Methods Detailed field sedimentological dissection and indoor microfacies analysis were conducted on the upper Cambrian Xixiangchi Formation in Chengkou town along the northern margin of the Upper Yangtze. Carbonate rock decimeter- and meter-scale upward shallowing sequences were identified， and their compositional characteristics and vertical superposition relationships were analyzed to explore the sedimentary environment and its evolution in the late Cambrian of the Upper Yangtze region. Results Based on detailed field observations and thin section identification， and referring to the Flügel sedimentary microfacies classification scheme， 14 microfacies types were identified in the Xixiangchi Formation at the Chengkou section， including subtidal sedimentary microfacies MF0-MF10； intertidal sedimentary microfacies MF11-MF12； and supratidal sedimentary microfacies MF13. These microfacies include： MF0 argillaceous shale， MF1 micrite， MF2 bright crystal gravel limestone， MF3 bright crystal sand limestone， MF4 muddy siltstone， MF5 dolomitic microcrystalline limestone， MF6 gravel dolomite， MF7 bright crystal sand dolomite， MF8 sandy gravel dolomite， MF9 sandy dolarenite， MF10 sandy dolomite， MF11 laminated dolomite， MF12 bamboo leaf-like gravel dolomite， and MF13 grain dolomite with dissolution pores. Based on microfacies interpretation and vertical stacking relationships， C1-1 to C1-6 decimeter-scale upward shallowing subtidal， C2-1 to C2-6 decimeter-scale upward shallowing subtidal to intertidal， and C3-1 to C3-2 decimeter-scale upward shallowing intertidal to supratidal sedimentary sequences were identified. These decimeter-scale upward shallowing cycles constitute three secondary transgressive-regressive sedimentary cycles， which from bottom to top， constitute the rapid transgression-slow regression upward shallowing sedimentary cycle of the Xixiangchi Formation. Secondary cycle I was developed by subtidal sedimentary microfacies， secondary cycle II was developed by subtidal to intertidal sedimentary microfacies， and secondary cycle III was developed by intertidal to supratidal sedimentary microfacies. From bottom to top， the thickness of subtidal sedimentary microfacies in the lower part of each secondary cycle decreases successively， whereas the thickness and exposure degree of intertidal to supratidal sedimentary microfacies in the upper part of each secondary cycle gradually increase. Conclusions Based on the identification of upward shallowing sedimentary sequences and the analysis of their compositional characteristics and vertical stacking relationships， the Xixiangchi Formation in the late Cambrian was significantly influenced by high-frequency sea level changes， strongly controlled by tides， waves， and storms. It experienced early rapid transgression and late slow regression， and underwent multiple secondary transgressive-regressive cycles， forming a limited carbonate platform sedimentation model characterized by mixed tidal flat subfacies， micritic lagoon subfacies， and intraplatform grain shoal subfacies. Furthermore， the development of paleo-weathering crust at the top indicates significant regression and erosion events in the late Cambrian in this region. By comparing with chronostratigraphic and evolutionary characteristics of platforms in the Yangtze Platform， North China Platform， Tarim Platform， United States， and Australia， it further confirms the global sea level fall events in the late Cambrian.