The Hadansun intrusive complex is situated at the south of the Mayinebo fault in the northeastern margin of the Junggar. It takes a form of triangle which is possibly contributed to faults. The main rocks of the complex are complicated, including gabbro, monzonite, quartz monzonite, diorite, monzonitic granite and potassic granite. SHRIMP UPb dating of zircon from monzonite indicates a crystallized age of 289.5±3.6Ma. Except several gabbro samples, the other samples are alkaline. The gabbro has a total REE content ranging from 43×10-6 to 86×10-6, and enrichment of LREE (LaN/YbN=2～6), with no distinct Eu anomalies. The contents of trace elements change consistently and LILE is also enriched with low Cr and Ni. The intermediate rocks have ∑REE higher than 100×10-6 and variable enrichment of LREE, and no Eu anomalies. The total REE content of the intermediate rock is more than 100×10-6, with various enrichment of LREE（LaN/YbN=6~20）and no distinct or weak Eu anomies. The intermediate rocks contain variable contents of trace elements, but generally have a similar variation trend such as systematic enrichment of LILE and depletion of HFSE. According to their REE characteristics, the granite samples can be subdivided in to two groups: one group, which is of weak Eu anomalies and highly enriched in LREE, shares similar trace elements distribution patterns with those of the intermediate rocks; the other group have significantly negative Eu anomalies (δEu=0.1～0.3), slightly enrichment of LREE and significant Ba, Sr, P, and Ti depletions on the trace elements distribution patterns. All the rocks from the Hadansun complex have very low initial Sr values (0.7036～0.7039) and coherent positive initial Nd values (~6.5). Combined with field observations, geochemical and lithological characteristics suggest that the gabbro may be derived from depleted mantle which was possibly metamorphosed by the subductionreleased fluid. The granite was derived from partial melting of the juvenile mafic lower crust at depth of 30～40 km, which resulted in that part of acid magma show natures of high Ba and Sr granite. Mixing of basic magma and acidic magma during moving up resulted in the formation of the intermediate rocks including diorite and monzonite. The Hardansun complex was formed at the postcollision tectonic setting. Magma mixing between the mantlederived and crustderived members was possibly of great importance to the Phanerozoic crustal growth.