In order to study the age of Xichangjing-Niujuanzi-Hongliuhe ophiolite belt in Beishan area of Gansu Province, the authors conducted zircon LA-ICP-MS U-Pb dating of gabbro from this ophiolite belt. The result shows that the weighted average ²⁰⁶Pb/²³⁸U age of this ophiolite is (446.5±4) Ma, suggesting late Ordovician. In combination with previous researches, the authors hold that Niujuanzi ophiolite and Hongliuhe ophiolite should be the products of early Paleozoic Ocean evolution. This study is of important significance for the study of tectonic evolution in Beishan area during early Paleozoic period.