In view of the discovery of Early Paleozoic microfossil group, the Dengshan Group Complex in Guangfeng-Shangrao district of northeastern Jiangxi is considered to be of Early Paleozoic. In this paper, the geology of oceanic volcanic rocks in Dengshan Group Complex is described, and the petrochemistry, geochemistry and genesis of Bazhukeng and Yejia volcanic rocks are studied. It is suggested that all volcanic rocks belong to island arc tholeiitic series, and are somewhat transitiona to oceanic tholeiitic series, being products of the expansion of the back-arc small oceanic basin. There are some differences between volcanic rocks of two formations in volcanic activites and magmatic evolution forms and degrees, which are consistent with the thinning of the oceanic crust from early to late stage.