The Yinzu pluton, one of the six large intrusions in southeastern Hubei Province, is the only barren large intrusion in the region. LA-ICPMS zircon U-Pb dating results show that the Yinzu pluton experienced at least two episodes of magmatism. The pluton is composed mainly of quartz diorites and was emplaced in 148±1 Ma, with the early biotite hornblende gabbro emplaced at 151±1 Ma. The study indicates that the Mesozoic magmatic activities in southeastern Hubei Province and even the Middle and Lower Yangtze River began in ca.150Ma. Based on their contact relation in the field and element chemical characteristics, the rock types of the Yinzu pluton can be divided into two groups. The first is diorite-gabbro, including diorite, biotite gabbro and biotite hornblende gabbro, which have low SiO2, Ba, Sr and high TiO2, FeOT, MgO, Y and Yb contents. The second includes quartz diorite and granodiorite porphyry, which have high SiO2, Ba, Sr and low TiO2, FeOT, MgO, Y and Yb contents. (87Sr/86Sr)i and εNd(t) values of quartz diorite are 0.70638～0.70719 and -9.56～-7.59, separately, which are coupled with zircon εHf(t) values ranging from -10.21 to -1.15. (87Sr/86Sr)i and εNd(t) and of biotite hornblende gabbro are 0.70742 and -9.79, separately, and zircon εHf(t) values vary from -24.58 to -15.22, showing that Nd and Hf isotopic compositions are decoupled. Combined with emplacement time and geochemical and Sr-Nd-Hf isotopic characteristics of two magmatic activities, it can be inferred that the pluton should be evolvement products of the same magmatic source area, i.e. from enriched lithospheric mantle. Fractional crystallization played a dominant role in the formation of quartz diorite. Nd-Hf isotope decoupling of the early small scale gabbros is probably related to the effect of garnet.