Long period stacking ordered type magnesium (LPSO-Mg) alloys have low density, excellent mechanical strength and ignition resistance. LPSO-Mg have a great potential as structural materials of satellites. Lip formation and ejecta size were examined when spherical projectiles strikes thin plates made of LPSO-type magnesium alloy at hypervelocity of 5 km/s. Witness plates were placed in front and behind of each target to determine the scattering area. After impact experiments, ejecta were collected from test chamber and lips near penetration hole was observed. Results of LPSO-type magnesium alloy plates were compared with those of aluminum alloy (A6061-T6).