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 the Paleozoic. In this paper, we report new zircon U-Pb age, 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) zircon U-Pb dating has revealed a crystallization age of 417.6±4.7 Ma for the HHS pluton. Alkali-feldspar syenite is the main rock type; Aegirine-augite and sanidine (An₀Ab_2~5Or_95~98) are the major minerals, with subordinate albite (An₀Ab_95~100Or_0~5). 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 (σ=8.48~11.09), high K₂O contents (8.66%~13.78%), 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=0.704 1~0.706 1) argue for an enriched subcontinental lithospheric mantle (SCLM) source 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 the Early Pleozoic, 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 microcontinent, the northern margin the NCC has entered into a temporary, post-collisional extension tectonic setting.