There are differences in the understanding of the tectonic background and the transition time of lithospheric mantle properties of the North China Craton during the Late Jurassic period. The author first discovered Late Jurassic diabase in Xuanhua District, Zhangjiakou City, on the northern edge of the North China Craton.The author conducted geological, petrological, geochemical, and isotopic dating studies on diabase, and and studied tectonic background.This article obtained a LA-ICP-MS zircon U-Pb age of 152.3±2.3Ma in diabase, dating back to the early Late Jurassic.The SiO2 content of diabase ranges from 48.99% to 50.43%, and K2O content ranges from 1.52% to 2.04%; TiO2 content ranges from 1.77% to 2.05%, with Rittman index σ=3.64 to 5.78,and magnesium index of Mg#=43 to 46, belonging to the alkaline basalt series within the continental plate. Total rare earth content ΣREE=211.55×10-6 to 261.36×10-6; LREE/HREE ranges from 11.36 to 12.11, (La/Yb) N=13.92 to 18.09, (Gd/Yb) N=2.44 to 3.12, with strong light and heavy rare earth fractionation and strong heavy rare earth fractionation; δEu=0.91 to 1.0, with weak negative europium anomalies to no anomalies.The Late Jurassic diabase was formed in the extensional environment within the continental plate and belongs to the oceanic island type mafic magmatic rock.The mantle source area of diabase is the oceanic primitive mantle modified by continental crust components.The Late Jurassic diabase in northwest Hebei Province was first discovered on the northern edge of the North China Plate, and is the earliest geological record of the retreat of the ancient Pacific Plate in the region.