The work aims to comparatively investigate the in-plane dynamic mechanics of regularly-arranged and alternately-arranged circular honeycomb cores based on finite element simulations. The FE models of two kinds of circular honeycomb cores were established by using Ansys/LS-DYNA under the in-plane impact loadings. By means of such simulation method, according to the analysis, the regularly-arranged circular honeycomb deformation modes, with the consistent structural parameters and different impact speeds, took on three stages, namely "X", "Y" and "I" shapes. The alternately-arranged circular honeycomb deformation modes were almost the same and took on "I" shape. The relationship between the conversion speed and the wall thickness radius ratio of the circular honeycomb deformation modes arranged in two ways was concluded. According to the FE simulation results, the empirical formulas of dynamic plateau stresses were derived in terms of configuration parameters and impact velocity. In conclusion, the in-plane dynamic mechanics of circular honeycomb cores arranged in two ways by means of FE simulation provide reference for the optimized design of circular honeycomb cores.