Nianzi rock unit in Beijing consists of East Shangtaizi，Nianzi and Xiaolianghou，output of which is along the Linhe—Jining—Shangyi—Chicheng—Gubeikou—Chengde—Pingquan deep fault belt，being a vital part for the early Mesozoic ganite belt in the Northern margin of NCC. Lithology compositions commonly is of medium—coarse and medium—fine grain porphyritic monzonitic. Zircon UPb dating of medium—fine granite，which is 247.5±0.62 Ma，reveals the Plutons formed in the Early Triassic. Accessory mineral compositions of the granite is the group of the magnetite，zircon，apatite and sphene. The monzogranite are characterized by high Sr and low Y，Yb，indicating adakite rock characteristics. Major elements analyses are presented enrichment in Si, alkali, and large iron lithophile elements(such as Rb, K, Ba). and depletion in Al, Fe, Ti, Cr, Ni, Ta, Zr，P，Ti. Chondritenormalized REE patterns suggests relatively LREEenriched and HREEdepleted，non extremely weak Eu negative anomaly. The characteristics above reveal that monzonitic granite in early Triassic belongs to the nodifferentiation Itype，metaluminous and highK calcium alkaline series. The magma likely originates from partial melted of the thickened mafic lower crust，which formed in Neoproterozoic. Meanwhile，the magma source region may remains garnet，hornblende and apatite. Monzonitic granite in Nianzi Unit formed in the process of structure extrusion environmental background，under which the northern margin of the North China craton and margin of the Mongolia hyper Craton had collided. The evolution of Central Asian organic zone has a great impact on the interior of the orogenic belt，simultaneously, has its strong influence on the north margin of North China craton，which caused a strong basement rock reconstruction.