We present a new approach to detect step initiation for the exoskeleton. Many studies for the exoskeleton have been done to detect step initiation by using EMG, Heel-off or Toe-off as soon as possible. This is, because, the detection of step initiation is not only starting point to activate the exoskeleton, but also a faster detection of step initiation enables the exoskeleton to assist the operator’s walking more quickly. In this paper, we detect step initiation faster than other approaches with vertical ground reaction forces. With our approach, the exoskeleton can not only detect step initiation faster, but also the exoskeleton assist the operator’s walking more quickly.