Black shale of the Lower Cambrian Niutitang Formation is widely distributed in the Yangtze Platform of South China, and there is regionally developed a typical conformable polymetallic sulfide horizon. A lower profile of the black shale enriched in Se, Mo and other metal elements in Xiaozhu of Zunyi area was selected for Se isotope determination so as to investigate the probable source of Se and its depositional environment. The results show that remarkable variation of δ82/76SeSRM 3149 exists in the studied black shale sequence. The middle carbonaceous shale, Ni-Mo layer and carbonaceous carbonate have a narrow range of δ82/76SeSRM 3149, from +0.65‰ to +1.15‰ with a mean of 0.91‰±0.23 ‰ (n=4); the upper carbonaceous shale has a value of －1.24‰; the bottom k-bentonite and phosphorite have a wide range of δ82/7SeSRM 3149 between －4.35‰ and +4.11‰. Combined with the publishedδ98/95MoJMC data of Ni-Mo layer in the Huangjiawan section, it is held that the middle black shale was deposited in an anoxic/euxinic environment,but an uncertain mixing process between basin seawater and oxic ocean water or hydrothermal fluid must have happened at that time. The bottom K_bentonite experienced a strong weathering and alteration, and the oxidization-reducing process probably occurred near the boundary between oxidizing water and anoxic water. Se in seawater might have been leached from the Se-rich bottom K-bentonite or tuff or from submarine hydrothermal fluid. Se isotopes indicate that the depositional environment of black shale in the Niutitang Formation of Zunyi area waspossibly situated on the continental margin of a stricted basin and experienced different evolution stages from dizing-suboxic-anoxic/euxinic to suboxic.