The Beishan orogenic belt is located on the southern margin of the Central Asian giant orogenic belt. It is one of the key areas for dissecting the accretionary tectonic process of the southern margin of the Central Asian orogenic belt. Researchers have a great controversy about the closing time of the Paleo-Asian Ocean and focus on whether the Devonian ancient Asian Ocean was still subducting or closed. This study firstly identified and a typical adakite characteristics pluton at Heishantou area on the southern margin of the Beishan orogenic belt. The geochemistry characteristics and zircon U-Pb chronology of the pluton were studied to discuss its genesis and geodynamic significances. The Heishantou pluton is dominated by granodiorite and partially consist of tonalite. The weighted average age of granodiorite LA-ICP-MS zircon U-Pb is (407.7±1.6) Ma. Geochemical data show that the Heishantou pluton belong to peraluminous, calc-alkaline series, with typical adakite characteristics: high silicon (SiO2=60.85%～67.81%), high alumina (Al2O3=15.59%～16.98%) , Low magnesium (MgO=0.55%～1.53%，Mg#=0.36～0.46), rich in sodium and poor in potassium (Na2O=2.65%～3.54%，K2O=1.09%～3.16%，Na2O/K2O=0.96～2.44), High Sr (Sr=253×10-6～487×10-6) Low Y and Yb (Y=5.65×10-6～16.70×10-6，Yb=0.37×10-6～0.96×10-6) , High Sr/Y value (Sr/Y=25.75～73.58); light rare earth elements(LREE) are enriched, light and heavy rare earth fractionation is obvious, the sample does not have obvious Eu anomaly (δEu=0.66～1.31, average 0.92); Moreover, trace element composition is characterized by enrichment(LILEs), such as Rb, K, Th, U, and depletion of high field strength elements(HSFEs), Nb, Ta, Ti, P. The geochemical characteristics show that these adakite formed by partial melting of the subducting oceanic crust and the residual minerals of the crust sources should be garnet and rutile. Based on our study and the regional geology data, we believe that the Liuyuan Ocean (Paleo-Asian Ocean) was still in the subduction and collision stage during the Early Devonian and had the characteristics of "scissoring" closure from west to east. The upper limit of the closing time of the Paleozoic ocean basin is Early Carboniferous. in the Beishan area.