Strong magmatic differentiation by fractional crystallization could significantly modify the apparent geochemical features of A- type granites, resulting in an ambiguous boundary between A- type and I/S- type granites. Thus, distinguishing between these types of highly differentiated granites presents a significant challenge. The Dawushan granitic intrusive body in the central Jiangxi Province could be an illustrative case to demonstrate methods for discriminating a highly differentiated A- type granite. The Dawushan granite, composed of medium- grained biotite monzogranite (phase I) and fine- grained muscovite- bearing biotite alkali feldspar granite (phase II), is located in center of the Cathaysia Block and the northern Nanling Range. Zircon U- Pb dating shows that the formation ages of phase- I and - II are 156 Ma and 155~157 Ma respectively. The Dawushan granite is characterized by low P2O5 (0. 05%~0. 16%), high SiO2 (70. 8%~74. 9%) contents, high Rb/Sr (averaging 9. 05) and Rb/Ba ratios (averaging 2. 38), and is weakly to strongly peraluminous. Plots in the triangular diagram of Rb- Ba- Sr and bivariate diagram of Th/Nd- Th suggest that the Dawushan granite experienced a high degree of differentiation. Other characteristics, 〖JP2〗such as high Ga/Al ratio (2. 89~3. 48), zircon saturation temperature (839 ℃), and anhydrous feature indicated by interstitial biotite aggregation suggest that it is an A- type granitic intrusion. Considering strong fractional crystallization of minerals enriched in zirconium, such as zircon and sphene, the Dawushan granite shows a linear trend distinctively different from the I/S- type granite on the diagrams of 10000×Ga/Al vs. Zr+Nb+Ce+Y and Zr vs. SiO2. In addition, its Y/Nb ratios are greater than 1. 2. Taken together, these characteristics suggest that the Dawushan granite belongs to a highly differentiated A2 granite rather than a differentiated I- or S- type granite. Therefore, on the basis of petrology, mineralogy and geochemistry analyses, the distinctive evolving trends shown on the diagrams of 10000×Ga/Al vs. Zr+Nb+Ce+Y and Zr vs. SiO2 by the I- & S- type and the A- type granites can be effectively used for identifying and discriminating between different primary rock types of highly fractionated granites. Isotopically, the Dawushan granite exhibits low εNd(t) (-9. 23~-14. 6) and εHf(t) values (-10. 2~-6. 5), and old two- stage Nd model ages of 1. 7~2. 0 Ga. Considering with the metamorphic rocks outcropped in this region, the Dawushan granite could have originated from a composite source consisting of orthometamorphic and parametamorphic rocks similar to the Zhoutan Group. In particular, such a source experienced an S- type melting extraction event during the Indosinian Period, leaving behind relatively refractory materials similar to diorite in composition. In the Yanshanian Period, the second melting event occurred in the residual source at higher temperatures with heat from the upwelling hot asthenospheric mantle under regional extension leading to the formation of the Dawushan A- type granite.