Weizhou Island in Beihai City of Guangxi is the largest Quaternary volcanic oceanic island in China. The latest eruptive product is basanitoid, which covers the tuffite strata of Late Pleistocene Huguangyan Formation (Q3h).It is worth mentioning that many peridotite xenoliths were found in the strata.They are distributed in the basanitoid pyroclastic flow with the unique form of volcanic breccia, quite different from normal xenoliths. As the xenoliths have experienced blasting, they might be called xenolith fragments. Obviously, such xenoliths constitute one of the most peculiar types of peridotite xenolith occurrence. The original xenoliths might have been dunite and harzburgite. Bothock structure and microprobe data show that these peridotite xenoliths were derived from the oceanic lithosphere mantle. The estimated equilibrium p-T conditions of xenoliths are about 1.3 GPa and 960～1040℃, with the corresponding stable depth being 40 km. Besides, the xenoliths came from a place much shallower than their host rocks, suggesting that they were accidental xenoliths. And they experienced blasting before emplacement.