Abstract: An adakite and Nb-enriched basalt association is found in early Devonian Group in north Junggar, Xinjiang, northwest China. This association is very important not only for studying the southward subduction of the Paleo-Asian Ocean, but also provides an ideal research project for evolution of northern margin of the Kazakhstan-Junggar Plate in Late Paleozoic. The geochemical results show that the geochemical characteristics of the andesitic rocks in this area are consistent with those of adakites. They have high Al203, Na20 and Sr contents, and high Sr/Y ratio. HREEE and Y in the samples are obviously depleted. M0RB-normalized trace element spider diagram shows negative Nb, Ta anomalies and remarkably positive Sr anomaly with very strong HFSE depletion. Their chrondrite-normalized REE patterns show no Eu anomaly and HREE depletion. The geochemical features of the associated Nb-enriched basalts are very similar to those of typical Nb-enriched basalts. They are Si02 overstraturated and Na-enriched, and are distinguishable from the typical arc basalts which are characteristic of high Nb, Ti, P contents, and HSFE enrichment. The projections of the adakites fall into the mantle array area that is defined by oceanic basalt in the 87Sr/S6Sr vs 143Nd/144Nd diagram. It means that the adakite was derived from the partial melting of the Palaeo-Asian oceanic crust, and the Nb-enriched basalt was originated by the partial melting of the mantle wedge which was slightly contaminated by the continental crust. Because the adakite and Nb-enriched basalt are related with ocean plate subduction, the distribution of the association in northern Junggar indicates that the Palaeo-Asian oceanic crest subducted southwards beneath the Kazakhstan-Junggar Plate in Early Devonian.