An method for forming wireless communications groups applied in a wireless communications system includes selecting g coordinators from n wireless communications devices around a base station, allocating remaining (n−g) wireless communications devices of the n wireless communications devices to the g coordinators to form g wireless communications groups, reselecting a coordinator from each wireless communications group to generate g updated coordinators, and allocating remaining (n−g) wireless communications devices of the n wireless communications devices to the g updated coordinators to form g updated wireless communications groups.