The work aims to study the in-plane impact properties of double-walled metal I-beam honeycomb cores. The finite element model of I-beam honeycomb cores was established by means of finite element software Ansys/ LS-DYNA and the CAE analysis was carried out. The different deformation modes were expressed by the I-beam honeycomb cores at different impact velocities. When other structural parameters of metal I-beam honeycomb cores were kept constant, the in-plane dynamic peak stresses were linearly proportional to the square of impact velocities. When the impact velocities remained constant, its in-plane dynamic peak stress was in exponential relation with the ratio of wall thickness to side length. In the meantime, the empirical calculating formula with respect to the ratio of wall thickness to side length and impact velocities of the in-plane dynamic peak stress of the metal I-beam honeycomb cores was obtained by fitting. The I-beam honeycombs have excellent structure and energy absorption ability. The study on the impact performance of I-beam honeycombs has important value of scientific research and engineering application.