LA-ICP-MS zircon U-Pb dating of gabbro in Sidingheishan mafic-ultramafic rocks yielded an age of (320.9±3.0) Ma, which indicates the emplacement age of Sidingheishan mafic-ultramafic rock. The zircon U-Pb age of the monzogranite (collisional granite) associated with the mafic-ultramafic rock is (369.2±2.7) Ma. Combined with previous studies of regional geology, the authors infer that the collision period was ended before the Early Carboniferous and Sidingheishan area entered into the stage of continental rift in Early Carboniferous. The result obtained by the authors is important for the study of the tectonic evolution in thilibri>s area.