The Chaiwa area of Tibet was located in the middle eastern part of the Tethys Himalayan structural belt, and a large number of nearly East-West trending mafic dykes were widely developed. These mafic dykes were of great significance for studying the geological structural evolution in this area. This paper has carried out systematic petrology, chronology, and geochemistry studies on the mafic dyke rocks in the Chaiwa area. The rock types of mafic dykes in Chaiwa area were mainly diabase and gabbro porphyrite. Zircon U-Pb geochronology revealed that the crystallization ages of mafic dykes are 146~145 Ma. The basic dykes in Chaiwa were enriched in Ti, Fe, and P elements, belonged to alkaline series and enriched in LREE, showing the feather of low SiO₂(47.20%~50.54%) and high Mg^# (39.78~53.79), which were relatively enriched in high field strength elements(Nb, Ta, Zr, HF, Th) and were similar to the geochemical characteristics of the OIB. These geochemical characteristics indicated that the Chaiwa mafic dykes were originated from the partial melting of the asthenosphere mantle and were formed in continental margin rift setting. Combined with the development of mafic rocks in regional volcanic province, it is considered that the mafic dykes in the Chaiwa area were the products of the Kerguelen mantle plume under the back ground of continental margin rift. Although the crystallization age of the Chaiwa dyke was earlier than the peak period of Kerguelen mantle plume activity(132 Ma), it might belong to the small-scale magmatic activity before the peak period of mantle plume.