Zircon U-Pb geochronology，petrochemistry of greyish green diorite porphyrite were used to discuss its genesis，emplacement age and relationship to the uranium metallogenic background in the eastern part of Longshoushan. The results showed that the rock is rich in aluminum，alkali and light rare earth elements and with the geochemical characteristics of high field strength element depletion. The rock belongs to the quasi aluminum high calc-alkaline series，and the source magma may be derived from the partial melting of the basic rocks in the lower crust. The age of the diorite porphyrite vein is（422.3±3.6）Ma. Considering the age of granodiorite penetrated by porphyrite vein，the formation of alkali metasomatite in the study area was inferred before 433～420 Ma. The diorite porphyrite vein distributed along the fault provided favorable geochemical barrier and metallogenic space for the later uranium mineralization. Therefore the diorite porphery vein filling fracture has good prospecting potential and can be used as one of the indicators in exploring deep alkali metasomatic uranium mineralization in the eastern part of Longshoushan.