Using cathodoluminescence（CL）imaging and LA-ICP-MS in site U-Pb isotope dating technigue，this paper presents zircon U-Pb dating for the gabbro from the Baihua igneous complex in Tianshui area，eastern Gansu pvovince and reveals interesting tectonic implication. Baihua igneous complex consists mainly of pyroxenite-gabbro（diorite）-diorite-quartz diorite. They form a complete comagmatic evolutionary series. The tectonics environment discrimination of trace element geochemistry reveals the igneous complexs formed in an island-arc setting. The LA-ICP-MS single-zircons U-Pb age of the gabbro from Baihua igneous complex is （449.7±3.1）Ma（MSWD=1.9），which shows that the forming time of the island-arc type magmatite in northern zone of West Qinling is Late Ordovician，also reveals that the timing of subduction of paleoocean basin represented by the Guanzizhen ophiolite and resulting island-arc-type magmatic activities is probably Middle-Late Ordovician.