The pre-pilot drillhole CCSD-PP1 of the Chinese Continental Scientific Drilling Project, with a depth of 432. 08 m, is located in the Donghai area in the southeastern Sulu terrane. The core samples are comprised mainly of paragneiss, granitic gneiss and ultramafic rock with minor intercalated layers of phengite-bearing kyanite quartzite and eclogite. All the analyzed paragneiss and granitic gneiss samples experienced amphibolite-facies retrogressive metamorphism. According to the whole-rock analyses, mineral inclusions in zircons and cathodoluminescence images, the granitic gneisses may be divided into two types. In the zircons in the first type of granitic gneiss samples form pre-pilot drillhole CCSD-PP1, many non-UHP mineral inclusions, comprised of Qtz + Phe + Ap, were identified from the core (C) through the mantle (M) to the rim (R) of zircon. All analyzed zircons show magmatogenetic features and are characterized by euhedral crystal shapes. The cathodoluminescence images show typical crystallization growth zoning from the core to the rim. These features indicate that the first type of granitic gneisses in pre-pilot drillhole CCSD-PP1 has not experienced UHP metamorphism. However, in the second type of granitic gneiss, a low-pressure mineral inclusion assemblage, mainly consisting of Qtz + Phe + Ab + Ksp + Ap, was identified in the core (C) of a zircon, while coesite or coesite-bearing UHP mineral inclusions were identified in the mantle (M) and rim (R) of the same zircon. These features suggest that the second type of granitic gneiss may have formed prior to UHP metamorphism and then together with paragneisses, phengite-bearing kyanite quartzite and eclogite experienced UHP metamorphism. This research is of great significance for an in-depth study of the subduction-exhumation mechanism and magmatism of Sulu UHP metamorphic belt and the selection of the drilling site for the Chinese Continental Scientific Drilling Project.