Abstract: The Zhangjiaba and Xinyuan plutons of South Qinling were formed in the Mesozoic. They have high Al2O3, K2O contents, and are relatively enriched in LILE and poor in HFSE, with high Sr （498 × 10^-6 -623×10^-6） , low Y （5.57 × 10^-6 -24 × 10^-6） and Yb （0.52 × 10^-6 -2.13 ×10^-6） and with slightly negative or positive Eu anomalies. All these demonstrate the features of high-K calc-alkaline granitoids formed by partial melting of lower-crust materials under the thickened crust. On the other hand, needle-shaped apatite and quenched-edge texture are well developed in the enclaves in both plutons. There is a visible composition gap between enclaves and granitoids. Two different magmatic evolutional trends correspond to two different REE patterns. These evidences imply that they were resulted from mingling of two-end-member magmas derived from different sources, suggesting that there was a crust-mantle interaction in the Mesozoic and an important vertical growth of crust in Qinling area.