The black rock series of Lower Cambrian are well developed in Chengkou district, Chongqing. ICP-MS techniques were used to analyze trace element contents in Lower Cambrian black rock series, including cherts, black siltstones and multi-elements concentrated layers. REE geochemical characteristics and their diagrams, high enrichments of Cr, Sb, As, Bi and U/Th ratios indicated that black rock series mainly formed by hydrothermal deposition. Meanwhile, the petrogenesis of black rock series was associated with volcanism, which provided the composition and dynamics to the hydrothermal activity.