Abstract: In this paper several early Sinian geological sections are selected to prove for the first time the existence of an ancient ophiolite belt in northeastern Jiangxi. Evidence is from the rock association, mode of occurrence and mode of emplacement of ultrabasic masses and some petrological characteristics. It is considered that the ultrabasic masses were the products of overthrusting by forceful tectonic action （i. e. cold emplacement） and did not result from mag- matic intrusion. From the base upwards the rock association of the ophiolites is ultrabasic rocks and diabase-intermediate-basic volcanic rocks-glauconite si- liceous rocks-flysch formation. Finally the paper gives a brief account of the basic characteristics of the paleoplate tectonics in northeastern Jiangxi. In early Proterozoic time, the flysch formation at the obducted side of the Yangtze paleoplate in this area was over ten thousand meters in thickness. By early Sinian time, the Yangtze paleoplate was compressed by the subduction of the "Pacific plate", bringing about the inversion of part of geosynclines in the Yangtze paleoplate and the formation of a continental fold mountain system--the Jiangnan ercuate uplift. In Mesozoic time, collision, compression and folding of continental crusts gave rise to a series of mountain systems. This paper proposes the existence of an ancient ophiolite belt and the process of evolution of the paleoplate in the hope of drawing attention from geological, geophysical and geochemical workers concerned.