In order to improve the occupant protection in coach rollover accident to reduce or avoid injury of occupants, according to the occupant's body motion behaviors, injury mechanism and injury level, an ARS (active-tilting restraint system) safty seat is originally proposed. A compound finite element model (FEM) combining coach body segmental structure, restraint system and occupant is developed via the items of ECE R66 to analyze and realize different occupant injury protection capability of the two kinds of seat restraint systems, with and without the ARS. The comparative calculation and analysis results express that during coach rollover the ARS seat effectively guarantees occupant motion within residual space, avoiding occupant body impact side going beyond it to be injured; and making HIC (head injury criteria) and TTI(thoracic trauma index) improved. The research concludes that the ARS seat can keep the occupants within the residual space preventing from impacting coach body by initiative pulling back against rollover to restrain the body's motion, and enhance occupant protection of coach body.