The Beishan orogenic belt is a key region for deciphering the accretionary processes of the southern Central Asian Orogenic Belt. Here in this paper we present new zircon U–Pb ages, bulk–rock major and trace element, and zircon Hf isotopic data for the Baitoushan, and Bagelengtai plutons in the western Central Beishan region to address the accretionary processes.The Baitoushan pluton consists of quartz diorites, monzonites and K-feldspar granites, with zircon LA–ICP–MS U–Pb ages of 435Ma, 421Ma and 401Ma, respectively. The Baitoushan quartz diorites and quartz monzonites exhibit relatively high MgO contents and Mg# values (63–72), display enrichments in LILEs and LREEs, and exhibit high Ba (585–1415ppm), Sr (416–570ppm) and compatible element (such as Cr and Ni) abundances, which make them akin to typical high-Mg andesites. The Baitoushan quartz diorites and quartz monzonites were probably generated by the interaction of subducted oceanic sediment-derived melts and mantle peridotites. The Baitoushan K-feldspar granites are ascribed to fractionated I-type granites with peraluminous and high-K calc-alkaline characteristics. They exhibit positive εHf(t) values (2.43–7.63) and Mesoproterozoic–Neoproterozoic zircon Hf model ages (0.92–1.60Ga). Those early Devonian granites, including Baitoushan K-feldspar granite and Gongpoquan leucogranites (402Ma), are derived from melting of the mafic lower crust and/or sediments by upwelling of hot asthenospheric mantle. The Bagelengtai granodiorites exhibit similar geochemical signatures with that of typical adakites, with a zircon SHRIMP U-Pb age of 435Ma. They exhibit relatively high Sr (502–628ppm) and Al2O3 (16.40–17.40wt.%) contents, and low MgO (1.02–1.29wt.%), Y (3.37–6.94ppm) and HREEs contents, with relatively high Sr/Y and (La/Yb)N ratios. The Bagelengtai granodiorites were derived from partial melting of subducted young oceanic crust, with significant contributions of subducted sediments, subsequently hybridized by the mantle peridotite.On the basis of our data and combined with previous data, we conclude that a Silurian–early Devonian slab window model accounts for all geological records in the western segment of the Central Beishan. We further propose that magmatic events associated with a slab window played an important role in crustal growth of the Central Asian Orogenic Belt.