Iron is pivotal in the global biogeochemical cycles and holds considerable significance for comprehending the surface environment and biological evolution during the early Ediacaran Period. This research concentrates on the cap carbonate of the Ediacaran Doushantuo Formation located in the Jiulongwan section of the Xiajiang region, southern China. Utilizing dilute acetic acid leaching to extract iron isotopic compositions from carbonate phases, the study reconstructs the iron isotopic evolution curve of early Doushantuo seawater, which exhibits a three-stage variation characterized by a decrease, an increase, and a significant decrease. During the deposition of the cap carbonate, the iron cycle was initially dominated by iron input from glacial meltwater, succeeded by the control of pyrite burial in the intermediate stage, and ultimately, the extensive burial of iron oxides in the late stage. The oxidation of water bodies in the later stage of cap carbonate deposition established a suitable ecological environment for the survival and development of microorganisms, thereby promoting biological evolution and radiation during the early Ediacaran Period. The dynamic changes in marine iron cycling during the early Ediacaran offer new insights into the interplay between environmental and biological evolution during this critical juncture in Earth''s history.