The Late Silurian to Early Devonian potassic alkaline rocks on the northern margin of the North China Craton (NCC) is a key geological unit to understand the interaction processes of the Paleo-Asian Ocean and the NCC in Paleozoic times. In this paper, we report new U-Pb zircon age data, mineral chemistry, whole-rock geochemistry and Sr-Nd isotopic compositions from the Late Silurian potassic Huangheshao (HHS) syenties on the northern margin of the NCC, and discuss its petrogenesis. Sensitive high-resolution ion microprobe (SHRIMP) U–Pb zircon dating has revealed a crystallization age of 417.6 Ma for the HHS pluton. Alkali-feldspar syenite is the main rock type; aegirine-augite and sanidine (An0Ab2-5Or95-98) are the major minerals, with subordinate albite (An0Ab95-100Or0-5). Aegirine-augites locally transferred into winchite or magnesio-riebeckite. The HHS syenites have high total alkali contents (Na2O+K2O=12.79%~15.30%)，high Rittmann index (δ=8.48~11.09), high K2O contents (8.66%~13.38%), and high K2O/Na2O ratios (2.10~9.07), suggesting their alkaline, potassic-ultrapotassic affinity. High Sr abundances and radiogenic Sr isotopic compositions (initial 87Sr/86Sr=0.7041~0.7061) argue for an enriched subcontinental lithospheric mantle (SCLM) for the HHS magmas，which was previously metasomatized by melts/fluids from the subducted sediments on the down-going oceanic crust. The development of the Late Silurian to Early Devonian potassic alkaline rocks on the northern margin of the NCC indicates that the Paleo-Asian oceanic slab had subducted beneath the NCC in early Pleozoic times, and the subducted materials metasomatised the SCLM, forming a phlogopite/K-amphibole–bearing, fertile mantle source. During the end of the Late Silurian to Early Devonian, due to the accretion or collision of a microcintinent, the northern margin the NCC has entered into a temporary, post-collisional extension tectonic setting.