Large quantities of Precambrian volcanic-intrusive complexes are distributed between the northern side of Jiangshao suture and the southern side of Jiangnan orogenic belt in northeastern Jiangxi Province. They consist mainly of Neoproterozoic volcanic rocks and felsic-mafic igneous complexes, of which the largest one is Gangbian body covering 120 km2 in Hengfeng County. This complex body can be divided into felsic, mafic and transitional rock units at the mapping scale. The age of the upper intersection point on the U-Pb incongruent curve of zircon from the felsic rocks is 822±4 Ma.The Nd model ages of various rocks from Gangbian complex body are different from each other: felsic rocks are 1.49～1.68 Ga; mafic basaltic rocks are 1.51～2.21 Ga; Nd model ages of gabbro are approximately the same as those of basaltic rocks, being 1.54～2.13 Ga; the calculated Nd model ages of transitive rocks are 1.58～1.90 Ga. Therefore, the fractionation of mafic rocks inthis body from the mantle must have occurred much earlier than that of the felsic rocks. Nevertheless, the Nd model ages of these transitive rocks contain some information on mutual mixing and mingling of the two end-member magmatic bodies. The authors obtained quite a few isotopic data for various rocks in Gangbian complex body:εNd(t=822) values of the felsic rocks are -0.8～-4.4,87Sr/86Sr(822) ratios are 0.7068～0.70549,εNd(822) values of the mafic basaltic rocks are -2.6～+2.3, and 87Sr/86Sr(822) ratios are 0.70387～0.70527 These data show that the source of the basaltic magma was close to the bulk earth, whereas the source of Neoproterozoic felsic magma in the complex was derived from the EMⅠ mantle characterized by themixing of mantle and crust. It is thus considered that northeastern Jiangxi area developed magmatic underplating in Precombrian, and this process played an important role in the formation of the mama of Gangbian complex. The formation of the felsic magma was controlled by the melting of the crust because underplating of the basaltic magma along the boundary between the mantle and the crust supplied thermal energy which was accumulated in the magma chamber; temperature of the diapiric felsic magma chamber decreased in company with increasing extent of crystallization and viscosity in the felsic chamber; the physical state of the felsic magma chamber also changed simultaneously in order of liquid→(soild + liquid)→solid. The liquid basaltic magma entered the felsic magma chamber through the lower crust, in which the physical condition was changing. Finally, the successive chemical mixing and mechanical mingling of the two end-member magma bodies and the intrusion of magma took place. The time of magmatic mixing is defined by the age of the upper intersection point on the U-Pb incongruent curve of the zircon, i.e., 822±4 Ma. Based on the data of the Nd model age (tDM) and the Nd enrichment coefficient (fSm/Nd), it can be concluded that the middle Proterozoic Jiangnan orogenic belt was accreted on the southern margin of the Archean land nucleus in Yangtze paleocontinent, and that the Neoproterozoic terrestrial volcanic-intrusive complex zone was later accreted on the southern side of the Jiangnan orogenic belt. At that time, the accretion of Yangtze paleocontinent drew to its end and its piecing together with the Cathaysia paleocontinent began. Therefore, the Neoproterozoic volcanic-intrusive complex zone including Gangbian complex body became the link of these two paleocontinents.