The Ziyunshan pluton, located along the Xiangzhong basin in Hunan, consists mainly of porphyroid monzonitic granite and two-mica granite, the former is located in the surrounding of the pluton and constitutes its main intrusive granite, while the later occurs in its interior and belongs to late intrusive granite. The dark-colored mafic enclave with magmatic textures is usually observed in the intrusive bodies. The emplacement time of the Ziyunshan pluton is determined by high-precision SIMS zircon U-Pb dating. The main intrusive granite is dated at 225.2 +/- 1.7Ma and 225.6 +/- 1. 4Ma and the late intrusive granite is dated at 227.0 +/- 2. 2Ma, thus both granitic rocks were basically contemporary and emplaced during the Late Indosinian. Both two types of granite in this study are rich in SiO2(,) Na2O and K2O, and depleted in CaO, MgO and A(12)O(3), and its A/CNK index are 0. 85 similar to- 1. 05 with high consolidation index, 3. 61 similar to 5. 05 for the main intrusive ganite and 4. 13 similar to 14. 06 for the late intrusive granite. Both granitic rocks are characterized by Rb, U, La, Nd, Zr enrichment, and Ba, Nb, Ta, Sr, P, Ti depletion; the chondrite-normalized distribution pattern of REEs is characterized by "V"-shaped pattern, obvious LREE-enrichment ((La/Yb)(N) 7. 35 similar to 11.7) and negative Eu anomaly (delta Eu = 0. 32 similar to 0. 70). The zircon isotopes of both granites display similar signatures, the epsilon(Hf) (t) values of the Ziyunshan pluton display similar signatures-10.0 similar to-1. 6, and its delta(18) O values fall in the range of 7. 8 similar to 11. 4. The t(DM2) model ages are estimated at 1. 22 similar to 1. 79 Ga. The major oxides for all granite samples display good covariant relationships, and are obviously distributed along I-type granite evolution line, indicating threr are a intrinsic genetic relationship between the main intrusive granite and the late intrusive granite, both are of highly-differentiated I-type granite. All samples are distributed along the magmatic mxing trend line but away from the crystallization differentiation trend line, combined with the Hf-0 isotope resluts, it is shown that the Ziyunshan pluton was derived from the re-melting of Lower Proterozoic crustal meta-greywacke of Yangtze craton, and mixed with some mantle-sourced magma. The intrusive granite was formed under post-collision tectonic background, indicating South China block was subjected to the influences by both Pacific plate and Indosinian block under extension-thinning tectonic environment in the Late Indosinian. Compared with other Indosinian granites in South China block, it is considered that the suture region of Yangtze block and Cathaysia block lies along "Youxian-Shuangpai" region in Hunan.