Abstract: The Mesozoic volcanic rocks in Yanshan area comprise a wide spectrum of rock types including calc-alkaline, high-K calc-alkaline and shoshonitic lava series. All these rocks show strong LREE, LILE enrichment and HFSE depletion as well as moderately enriched Sr-Nd isotopic compositions, which are different from the mafic volcanic rocks within North China craton and from Xingmeng Orogen. The Yanshan volcanic rocks show transitional geochemical and isotopic signatures when compared to the Mesozoic counterparts in the adjacent cratonic area and orogenic belts, e. g., La/Nb, （Nb/La）N, （Hf/Sm）N ratios and end values, indicating that the melting mantle source of these rocks was modified by the subducted Paleo-Asian Ocean Plate on the basis of inheriting characters of EMI mantle within North China craton. Similar to lithospheric thinning and replacement mechanism, subductionrelated metasomatism of Paleo-Asian Ocean Plate played an important role during lithospheric thinning and evolution beneath Yanshan area, which is different from lithospheric thinning and replacement mechanism within North China craton