Abstract: The petrological study of Middle Devonian sandstones and conglomerates in Boyang area, Western Qinlingorogenic belt indicates that their composition maturity and structure maturity are very low, with the characteristics of the proximal deposit. In addition, the conglomerate has a few of the mylonitic gravels. The clastic zircons of sandstone interbeds from the Middle Devonian conglomerate in Boyang area are characterized by magmatic zircons. By clastic zircon LA-ICP-MS U-Pb dating of the sandstone interbeds, the age spectra of clastic zircon can be divided into 4 groups:①440~480 Ma, accounting for about 3%; ②540~600 Ma, accounting for about 4%; ③880~1 020 Ma, accounting for about 79%; ④1 040~1 080 Ma, accounting for about 13%. The age of 880~1 020 Ma shows the strongest peak, which is in accordance with the age of the Jinning period of Neo-proterozoicmagmatism in the Western Qinlingorogenic belt, and also is in accordance with age of the Rodinia supercontinent aggregation event. Integrating with the regional geological material, it is proposed that a significant tectonic uplift-erosion existed in the studied area during Middle Devonian. The clastic sediments of Middle Devonian strata mainly came from both of the Western Qinling and the Northern Qilian orogenic belt, so it is deduced that no longer exists deposition barrier zone in the area between the studied area and the Western Qinlingorogenic belt during Middle Devonian, and both of the Qinling and Qilian orogenic belts were possibly really amalgamated.