The Yiwulüshan metamorphic core complex (MCC) within the northern margin of the North China Craton is a typical representative of large-scale Mesozoic extensional deformation in Northeast Asia continent. Many studies including the fabric characteristics, shear-sense indicators, strain, kinematic vorticity and deformation age have been intensively conducted. However, some problems concerning geochemistry, isotopic characteristics and genesis of the granite within the core of this MCC remain unanswered. The granite of the core within the MCC is composed of biotite monzogranite and granodiorite. Based on previous research, together with the major elements,trace elements and Sr-Nd isotopic data, the paper presents the results of the data and discusses the genesis and geological significance. According to the results obtained, the granite of Yiwulüshan MCC granite is characterized by high silicon and alkali content (SiO₂ =61.17%~75.21%, K₂O+ Na₂O=7.34%~9.03%), thus belonging to metaluminous and peraluminous (A/CNK=0.96~1.08) and can be assigned to genetic type of high-k-calc-alkaline series, suggesting characteristics of I type granites; most granites have weak negative Eu anomaly (δEu=0.71~1.63), enrichment of large ion lithophile elements (e. g., Rb, Ba and Sr) and light rare earth elements, depletion of high field strength elements (e. g., Nb,Ta and Ti) and heavy rare earth elements, high Sr (308×10^-6~1 414×10^-6, averaging 709×10^-6), low Y (3.17×10^-6~13.30×10^-6, averaging 7.86×10^-6) and Yb (0.45×10^-6~1.32×10^-6, averaging 0.78×10^-6), showing the characteristics of adakitic rocks; isotopic data show that the early co-emplacement granites have a wide range of (⁸⁷Sr/⁸⁶Sr)_i values (0.695 966 ~ 0.707 869) and a lower εNd(t) values (-21.72~-18.32) and were derived from ancient crust and attributed to the partial melting of the thickened lower crust under the background of regional extension; the isotopic data of the later post-emplacement granites range from 0.705 909 to 0.706 774, and have negative εNd(t) values (-20.60~-16.99), which indicates that the post-emplacement granite resulted from the North China Craton extension thinning during the Late Mesozoic.