The 802.11 families are considered as the most applicable standards for Wireless Local Area Networks (WLANs) where nodes make access to the wireless media using random access techniques. In such networks, each node adjusts its contention window to the minimum size irrespective to the number of competing nodes. So in the case of large number of nodes, the network performance is reduced because of raising the collision probability. In this paper, a game theory based method is being proposed to adjust the users’ contention window in improving the network throughput, delay and packet drop ratio under heavy traffic load circumstances. The system performance, evaluated by simulations, shows some superiorities of the proposed method over 802.11-DCF (Distribute Coordinate Function.