In dynamic coastal ecosystems, such as a salt marsh wetland, seasonal changes can play important roles in the biogeochemical cycle of redox-sensitive metals (RSMs). This paper examines the main mechanisms influenced by seasonal changes on the biogeochemical cycle of RSMs (e.g., Fe, Mn, Mo, V and U) in salt marsh wetland. The samples were collected from the salt marsh wetlands of the Yellow River Estuary under different seasons and the growth condition of plants (Phragmites australis, PA). The RSMs concentration of porewater in different depth (0-40 cm) were determined. The results indicate that the tidal inundation, plant growth and decay with seasonal cycle were the main impacts on the RSMs concentration in porewater of the salt marsh wetland. These processes can directly or indirectly induce the variability of RSMs concentration in porewater through the establishment of oxidative or reducing conditions. The ingestion of RSMs in the PA growth stage and the release of RSMs after the PA decay stage can also affect the RSMs concentration in porewater. A representative example is Mo. Moreover, the bioturbation can induce the formation of oxidative conditions, resulting in the variability of RSMs concentration in the porewater of the salt marsh wetland. This study can provide basic data for the study of nutrient cycling in the salt marsh wetland, as well as a new sight for studying the response of other RSMs to environmental changes in the salt marsh wetland.