Molecular simulations using the molecular dynamaic method have been carried out to investigate the dynamic properties of the non-adsorbed Knudsen molecules in the overlapping sphere pore model. Knudsen pore diffusivities, mean collision times, pore-size distributions, velocity autocorrelation functions, mean-square displacement curves were computed over a wide range of porosity, Ψ≥0.1. Simulation data were used to assess the applicabilities of theoretical calculations reported in the literature. The simple Boltzmann approximation was found to be applicable only for the systems of higher porosity, Ψ≥0.8, whereas the extended kinetic equation based on multi-collisional density expansions has proven to be successful to predict Knudsen diffusivities in the range of Ψ≥0.3. The additional simulation results obtained in this work were used to elucidate detailed microscopic information on the distribution and dynamic effects of such pore systems at a molecular level.