Abstract: This work apply in situ extended X-ray absorption fine structure(EXAFS) to reveal sorption speciation of Np(Ⅴ) on synthetic lepidocrocite(γ-FeOOH). Np L_Ⅲ-edge EXAFS analysis shows that Np(Ⅴ) is absorbed on γ-FeOOH as neptunyl ion, with no observations of multinuclear surface complexes or surface precipitates. The Fourier transform（FT） magnitude of the EXAFS also shows an obvious peak feature at about 3 Å (1 Å =0.1 nm), that can be attributed to a Np-Fe scattering path, consistent with the formation of an inner sphere Np(Ⅴ)-lepidocrocite surface complex. The EXAFS FT results were compared between Np(Ⅴ) speciation on difference iron mineral phases with similar compositions. However, it remains a question whether or not a Np-C coordination exists, indicating the possible presence of Np(Ⅴ)/carbonate species on the lepidocrocite surface. Additional studies are needed, particularly well-designed EXAFS studies, to answer this question and verify the identity of the surface complex.