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Radioactivity levels of ²¹⁰Pb and ²²⁶Ra were detected in a sediment core obtained using a multi-corer from the polymetallic nodule area inside the Clarion-Clipperton Zone (CCZ), a contract area of the China Ocean Mineral Resources Association (COMR) in the eastern Pacific Ocean. The profile of excess ²¹⁰Pb (²¹⁰Pb_ex) shows that the specific activity of ²¹⁰Pb_ex has three parts with different distributions at depths of 0–16 cm (I), 17–36 cm (II), and 37–48 cm (III). When the I section of nonlocal mixing was excluded, using a steady-state diffusion mode, the bioturbation coefficients of the core were estimated to be 24.2 cm²/a at 17–36 cm deep and 5.9 cm²/a at 37–48 cm deep, which were greater compared to previously published results. This is most likely owing to bioturbations caused by various organism species in the two sections.