Iron as one of the highest abundance elements in the crust, plays a very important role in the marine sediment diagenesis. Iron as a nutritive elements in marine primary productivity, affects the input of organic matter in marine sediments; the coupling of iron sulfide and phosphorus can promote or reduce the organic matter burial; During early diagenesis, iron in marine sediments can alter the chemical properties of the pore water, resulting in aragonite grain dissolution, thereby affecting the cementation of carbonate sediments; Diagenetic alterations of iron minerals driven by anaerobic oxidation of organic matter have an important influence on the magnetic properties of marine sediments, producing secondary magnetic signal or weakening them; Isotope fractionation during dissimilatory microbial iron reduction, can indicate the biogeochemical cycle of iron and the redox conditions of ancient oceans. Processes mentioned above relate to the input of terrigenous detrital and the metabolism of organic matter, requiring further studies. These studies will have important significance to the related research, such as Oceanic Anoxic Events, the formation mechanism of marine source rocks and the model of carbonate precipitation and global carbon cycle.