Abstract: In the L. variegatus, Se-Met and Se-Cys were the main Se species. The benthic model organism, Lumbriculus variegatus, was used to quantify the content and morphology of selenium in the Lumbriculus by ICP-MS after 21 d exposure to environmentally relevant concentrations of the sedimentary phase Se(Ⅳ). The results showed that selenium could effectively accumulate in the Lumbriculus at environmentally relevant concentrations, and the morphology was mainly dominated by Se-Met and Se-Cys. In addition, Se at environmental related concentrations in the sediment increased the oxidative stress, inhibited the activities of Na⁺/K⁺-ATP enzyme and digestive enzymes of L. variegatus, inducing the decrease of condition factors and bioaccumulation. The results shed a light on the Se species, biological accumulation and effect of Se(Ⅳ) in sediments in the benthos, and provide theoretical basis and fundamental data for the bioaccumulation and effects of selenium in sediments.