Two large particle diamonds were selected from the Bailushan rock pipe during recent primary diamond prospecting in northern Jiangsu. The diamonds are of type ⅠaB and ⅠaA respectively and their particle sizes are greater than 1 mm. They are the first large particle primary diamonds discovered in the northern Jiangsu. In this paper, based on petrology, rock geochemistry, zircon U- Pb isotope age, and diamond characteristics of the Bailushan rock pipe, the genesis of the rock pipe is inferred and its relationship with diamonds is discussed. The result shows that the morphology of the Bailushan rock pipe reflects the characteristics of the fissure- central eruption of the hidden explosion volcanic rock pipe. Its main lithology is olivine basalt and its breccia composition includes olivine basalt, limestone, tuff, lamprophyre and breccia. Olivine basalt has the characteristics of high magnesium, low aluminum and low titanium. These characteristics are similar to the Ocean Island Basalt as the lithophile elements and light rare earth are enriched, but high field strength elements and heavy rare earth are slightly less. However, there is a strong Nb negative anomaly feature that is similar to the Island Arc Basalt. It was formed against the background of Meso- Cenozoic Pacific plate subduction and the lithospheric thinning of the North China Craton. The lithospheric mantle originated from a depth of about 75~100 km and was replaced by subduction fluid. It was partially melted from 2%~5% hornblende garnet diorite in the spinel stability zone and has suffered a certain degree of crustal contamination, separation and crystallization during magma evolution. Subsequently, olive basalt magma intruded into the shallow crustal formation along the weak structural zone under the environment of rapid tension in the plate. A large amount of surrounding rock breccia was captured during the ascent. Diamonds are not a crystalline product of olivine basalt in Bailushan. They may be from the captured Paleozoic diamond- bearing parent rock covered by the arcuate tectonic of the Xuzhou- Suzhou.