An occupant safety system using an optical fiber grid sheet and a method thereof are provided. The occupant safety system applies light to optical fibers constituting an optical fiber grid which is attached to a moving body and in which the optical fibers are arranged in a grid pattern; receives the applied light through the optical fibers; grasps a location of impact on the moving body based on the received light receiving signals; and controls operations of safety devices provided in the moving body based on the grasped location of the impact. Accordingly, the occupant safety system can sense impacts on the moving body everywhere through the optical fiber grid, and can exactly grasp the location of the impact and can drive an appropriate safety device timely. Therefore, the occupant can be protected safely.