Previous studies on basaltic trachyandesite were weak, and there was insufficient research on the lithospheric mantle characteristics of the North China Craton during the transition period of the Middle—Late Jurassic. Methods: The author conducts geological, petrological, and geochemical studies on the basaltic trachyandesite of the Tiaojishan Formation in Xuanhua District, Zhangjiakou City, northwestern Hebei, on the northern edge of the North China Craton, and studies its rock genesis and mantle source area. Results: The SiO2 content of basaltic trachyandesite is 48. 73% to 53. 23%, the MgO content is 2. 78% to 3. 79%, the TiO2 content is 1. 65% to 1. 93%, and the Mg # is 35 to 43. The basaltic trachyandesite belongs to the alkaline basalt series. Conclusions: The basaltic trachyandesite of the Tiaojishan Formation in the Middle—Upper Jurassic was formed in the early Late Jurassic and underwent separation crystallization of clinopyroxene and plagioclase, as well as crustal contamination. It was formed by low degree partial melting (1%~5%) of primitive mantle containing amphibole spinel garnet pyroxene rock, and was subjected to metasomatism of ancient Pacific subduction plate melt. The subducting plate melt explained originates from oceanic plate melt with the age of less than 25 Ma. Basaltic trachyandesite represents the early Late Jurassic period in which the lithospheric mantle of the northern margin of the North China Craton was mainly altered by the subduction of the Ancient Pacific Ocean. transforming from the Depleted mantle to Primitive mantle. The lithospheric mantle of the North China Craton in the Middle Late Jurassic evolved from the depleted mantle replaced by enriched components of the ancient Asian oceanic crust to the primitive mantle replaced by the melt of the ancient Pacific subduction plate.