Abstract: The magnetism of ZZ-GNR represents a pivotal topic in carbon-based spintronics. In a recent study, we experimentally verified the presence of intrinsic magnetism in ZZ-GNR by embedding them within a hexagonal boron nitride (hBN) lattice (Nature Materials, 2025, 24: 1592-1599). However, prior SNVM measurements only captured the magnetic field's projected component along the NV center axis, complicating the direct visualization of magnetic anisotropy characteristics through imaging. Building upon our previous findings, this paper introduces a magnetic field vector reconstruction method based on Fourier transform. By applying the constraints of Maxwell's equations in current-free regions, we successfully reconstructed the three-dimensional vector stray magnetic fields (B_x, B_y, B_z) of ZZ-GNR from the original Full-B mode data. Quantitative analysis reveals that the stray magnetic field generated by the ZZ-GNR edges is predominantly oriented in the out-of-plane direction (B_z), with a peak intensity of approximately 3.7 Gauss, while the in-plane components are minimal. Supported by control experiments on armchair graphene nanoribbons (AC-GNR) and empty trenches, this study provides direct confirmation of the pronounced perpendicular magnetic anisotropy of embedded ZZ-GNR at the nanoscale, offering crucial quantitative experimental evidence for understanding their ferrimagnetic ground state.