///Sulfur and selenium isotopic composition of two Ni-Mo-Se ore layers from Zunyi and Zhangjiajie were analyzed to understand the oceanic environment and origin of these Lower Cambrian polymetallic layers in South China. Sulfur isotopic difference suggests that there are different environments for these two ore layers. Ni-Mo-Se ore layer of Zunyi was formed under the environment of open ocean in which sulfate was intermittently inputted, and that of Zhangjiajie formed under more depleted oxygen closed environment. Selenium isotopic composition indicates that Se (-II) derived from hydrothermal fluids could have undergone oxidation-reduction recycling at the bottom host black shales and carbonaceous cherts. The parts of Se enriched in Ni-Mo-Se ore layers were controlled by adsorption of organism and clay minerals and isomorphism processes.