The Luchuan-Bobai metallogenic belt is an important W-Mo metallogenic belt in the southeast of South China. Several medium- to large-size W-Mo deposits associated with the Cretaceous composite granites, such as Michang, Andong, Youmapo and Sachachong, have been discovered in the belt. In this paper, we report new U-Pb ages, and petrological, geochemical and Sm-Nd isotopic data for the Michang and Andong plutons. The Michang pluton is composed of medium-coarse-grained hornblende biotite granodiorite with mafic microenclaves (MMEs) and medium-coarse-grained biotite monzogranite, which were emplaced at 113.7±0.3 Ma and 107.6±0.3 Ma, respectively. We suggest that the hornblende biotite granodiorite originated from a magma mixing process between felsic magma derived from melting of the Meso-Proterozoic mafic basement rocks and mantle-derived mafic magma. The age gap of 6 Ma between the biotite monzogranite and hornblende biotite granodiorite indicates that they were not derived from the same magma chamber. This is supported by the Nd isotopic data that the εNd(t) values of the hornblende biotite granodiorite (-1.7) is much higher than the biotite monzogranite (-5.8~-3.1). The Andong pluton (biotite monzogranite) which are peraluminous (ACNK = 1.18~1.25) have high K2O/Na2O ratio (1.92~2.40) and high Th and U contents. The εNd(t) values of the Andong pluton range from -4.0 to -3.8. We argue that the Andong pluton originated from a magma mixing process between felsic melts derived from partial melting of the Meso-Proterozoic metagreywackes and mantle-derived mafic melts. The lithospheric extension of the Cathaysia block in the Cretaceous resulted in the upwelling of asthenosphere and formation of basaltic magma that underplated and triggered partial melting the basement rocks, forming the multiple plutons in the Luchuan-Bobai metallogenic belt. From 113 Ma to 100 Ma, the Michang hornblende biotite granodiorite, "the Michang biotite monzogranite the Youmapo granodiorite the Andong monzogranite", the Sachachong pluton and the Youmapo muscovite granite were formed successively. Correspondingly, the εNd(t) values of the granites decrease gradually from early to late stages. The late-stage Sanchachong fine-grained muscovite-biotite granite and the Youmapo fine-grained muscovite granite (high silica, alkali, fluorine contents and low εNd(t) values) played a significant role in W-Mo mineralization and are of great mineralization potential.