Abstract: In this study,the stable carbon and nitrogen isotopic compositions of Apostichopus japonicus in the Bohai Sea and the Yellow Sea were performed by elemental analyzer coupled to a stable isotope ratio mass spectrometry (EA-SIRMS).Moreover,the contribution rates of potential food sources to the growth of A.japonicus were also calculated in order to study the stable isotope composition characteristics of A.japonicus in different seas and analyze the reasons.Results showed that δ¹³C and δ¹⁵N values of A.japonicus from the Bohai Sea ranged from -15.660‰ to -12.027‰ and 7.463‰ to 11.238‰,while that of A.japonicus from the Yellow Sea ranged from -16.062‰ to -12.527‰ and 3.966‰ to 7.243‰,which indicate that δ¹⁵N could clearly distinguish samples of A.japonicus between the Bohai Sea and the Yellow Sea.The contribution rates of potential food sources to the growth of A.japonicus from the Bohai Sea in descending were Plankton,SOM,POM,Laminaria japonica and Ulva pertusa,while that in the Yellow Sea were Ulva pertusa, Laminaria japonica,POM,SOM and Plankton.The difference of contribution rates provided an explanation for the difference of δ¹⁵N of A.japonicus between the two seas.The conclusion in this study will provide a theoretical basis for tracing the geographical origin of A.japonicus using stable isotope ratio mass spectrometry technology.