Authigenic pyrite is the normal product of anoxic sulfate reduction in marine sediments. Core HD196A, recovered from the seafloor of the northeastern South China Sea, has large amount of pyrites. The morphologies of pyrites are as the form of rod with hollow or not. The intervals around 500 cm of Core HD196A are enriched in authigenic pyrites, showing a rich zone of pyrites. Further studies show that the pyrite-enriched zone is consistent with the content boundaries of organic carbon, sulfate, methane and carbonate, where organic carbon, methane and carbonate increase downward, but sulfate starts to decrease sharply. The pyrite-enriched zone, combined with the content boundaries of organic carbon, methane, sulfate, and carbonate, show a sedimentary or geochemical change of Core 196A. Anaerobic methane oxidation and anoxic sulfate reduction contributed to pyrite formation, respectively. Large amount of pyrites occurrence can be a possible evidence of methane anomaly in marine sediments.