Lots of diabase and gabbro in the Suli area of the west segment of middle Qilian invaded into the Proterozoic geological bodies in the form of dykes. The previous studies of the basic magmatic rocks in this area were relatively insufficient and hence there are rare relevant reports. The content of SiO₂, Al₂O₃ and TiO₂ in the basic dyke are 46.77%～52.37%, 12.82%～15.86% and 1.16%～3.14%, respectively, characterized by high MgO (3.84%～7.98%) and FeO^T(10.42%～15.53%), and poor K₂O (0.10%～1.60%) and P₂O₅ with Na₂O higher than K₂O. The total rare earth content of the whole rock is low (51.28×10^-6～165.11×10^-6), the ratio of light rare earth to heavy rare earth is between 2.67 and 4.90, and the (La/Yb)_N ratio is between 2.04 and 5.03. The rocks are of light rare earth enrichment type, Eu=0.93～1.12, without obvious Eu anomaly. They are characterized by enrichment of Rb, Ba, Th and U and depletion of Nb and K; in addition, large ionic lithophile element abundance range is relatively wide, high field strength element enrichment degree is not strong, and trace element ratio on the cobweb diagram exhibits the pattern of an uplift on the left and relatively flat on the right, with the geochemical performance exhibiting the obvious characteristics of intraplate basalt. The LA-ICP-MS zircon U-Pb age is 819.5±5.2 Ma, and its formation age is older than that of the global Rodinia supercontinent. The results of rock geochemical analysis show that the magma originated from depleted mantle source area, probably being the product of partial melting of spinel mantle peridotite. The magma was formed in an intracontinental rift environment, indicating that it may have been the product of the breakup of Rodinia supercontinent.