Stable carbon isotopic compositions of n-alkanes in surface sediments of the Bohai and North Yellow Seas were inves-tigated to elucidate sources of sedimentary organic matter in these seas. The long-chain n-alkanes in surface sediments are predomi-nantly long-chain C27, C29, and C31 types, with obvious odd carbon predominance. The δ13C values of long-chain n-C27, n-C29, and n-C31 alkanes are -30.8％ ± 0.5‰, -31.9％ ± 0.6‰, and -32.1％ ± 1.0‰, respectively, within the range of n-alkanes of C3 terrestrial higher plants. This suggests that sedimentary n-alkanes are derived mainly from terrestrial higher plants. Compound-specific carbon isotopic analysis of long-chain n-alkanes indicates that C3 terrestrial higher plants predominate (64％–79％), with angiosperms being the main contributors. The n-alkane δ13C values indicate that mid-chain n-alkanes in sediments are derived mainly from aquatic emergent macrophytes, with significant petroleum pollution and bacterial degradation sources for short-chain n-alkanes.