In this work, the high frequency and microwave absorption properties of two-dimensional (2D) Sm2Fe14B nanoflakes were investigated. Both planar magnetocrystalline and shape anisotropy was obtained for the 2D Sm2Fe14B nanoflakes prepared via die-upset process, which can effectively increase the effective out-of-plane anisotropy field and improve the high frequency intrinsic magnetization (the product of initial permeability and resonance frequency). The nanoflakes have a diameter of approximately 1–2 μm and a typical thickness of approximately 200 nm. Compared with irregular Sm2Fe14B powder, a higher complex permeability and a lower complex permittivity were obtained for the 2D Sm2Fe14B nanoflakes because of the suppressing eddy effect and the oxidized grain boundary phase (GBP) layer, which facilitates the microwave absorption performance. A minimum RL value reaches −16.9 dB at the perfect matching frequency of 12.1 GHz.