Abstract: Element Analyzer-Isotope Ratio Mass Spectrometer (EA-IRMS) technology was applied to determine organic carbon stable isotopes of marine sediment. Pure CO₂ reference gas was calibrated via GBW 04408, and the δ¹³C_vsPDB value of pure CO₂ was determined to be -32.053‰. The stability and linearity of the EA-IRMS system were tested and verified through several experimental comparisons. The standard deviation of stability was 0.009‰. When ion intensities ranged from 0.4 to 8.7 V, the linearity of EA-IRMS system was 0.0337‰/V which was less than the requirement of linearity proxy of 0.06‰/V. Moreover, the precision and accuracy of the results for the national standard material of GBW 04408, international standard material of Urea and marine sediment sample of M01 were measured. The standard deviation was 0.13‰. The marine sediment samples were measured at three different labs. The standard deviation of the comparison results was less than 0.20‰ and met the need of reproducibility of 0.5‰. The TOC contents from marine sediment samples ranged from 0.13‰ to 1.11‰, with δ¹³C_org values ranging from -25.29‰ to -22.30‰, which indicate the derivation of organic matter from mixed terrestrial and marine organic materials.