We presented a new finding that the occurrences of oceanic redbeds in the South China Sea (SCS) first discovered from Expedition 349 are similar to those in Sulu Sea and Celebes Sea from Expedition 124, as well as to the continental redbeds in Sanshui Basin of China, all directly covering massive magmatic rocks with significance for revealing the connections between oceanic redbeds and magma thermal events. We measured the samples collectted from marine sedimentary with colors ranging from celadon to rufous in U1434 of IODP Expedition 349, and analyzed the influence of oxygen fugacity and geothermal temperature on the formation of pigment in redbeds. By comparing red-nonred sediments and experimental samples, we discussed the redbed genesis and its geological implications. We obtained the red values, the content of goethite, hematite and quantivalent Fe in marine sediments and experiment samples through the analysis of diffuse reflectance and fluorescent spectroscopy and Fe2+ in titration test. The results showed that, (1) Red and non-red marine sediments are formed at high oxygen fugacity environment in U1434 of IODP Expedition 349, and difference in oxidation-deoxidation environment was not the controlling factor on red and non-red sediments; (2) The oceanic redbeds directly covering basalts in U1434 of IODP Expedition 349 originated from high geothermal temperature during sedimentary- diagenesis process; (3) And we found that continental redbeds and Cretaceous oceanic redbeds formed in different geological periods are closely associated with tectonic- magmatic active belts, showing that redbeds have significance in indicating geological thermal events.