The essence of crashworthiness is to study the protection of people（ crew and passengers）,and the head injury of the occupants accounted for a large proportion in the crash. In order to investigate the influences of different impact velocity on the occupant ’s head injury under horizontal impact conditions,a comprehensive evaluation method based on occupant ’s Abbreviated Injury Scale（ AIS） and occupant’s injury risk probability to evaluate occupant injury is proposed,and a dynamic simulation model which including seat,restraint system and dummy was constructed by LS-Dyna software. Take the typical civil aircraft double-tube triple-seat as research objects,the effects of different horizontal impact velocity（ 8. 0 m/s,10. 0 m/s,12. 0 m/s,14. 0 m/s,16. 0 m/s） on the head injury of occupants,the stages and characteristics of injuries were analyzed. The results of dummies‘ dynamic response analysis shows that occupants may be severely injured in the head and legs during the aircraft’s longitudinal impact,occupant’head injury increases rapidly with the increase of horizontal impact velocity,and occupant’fatality rate increases exponentially with increasing horizontal impact velocity,the substantial leg movement of the occupants greatly increase the risk of injuries caused by collisions with other facilities in the cabin. In addition,the dummies ’ head trajectory,the peak load of seat belt is proportional to the horizontal impact velocity. Therefore,when the crash occurs,the horizontal impact velocity should be controlled deliberately（ the fatality rate was less than 10% when the impact velocity was13. 0 m/s,and more than 80% when the impact velocity was 16. 0 m/s）.