In IEEE 802.11 wireless networks, as the number of network nodes increases, impact increase accordingly, channel utilization decreases, and aggregate throughput decreases, resulting in system function degradation. In response to this problem, this article proposes a solution: number nodes-based minimum contention window dynamic adjustment (NNMCWDA), which dynamically adjusts the minimum competition window to achieve channel resources' rational allocation. Simulation tests have shown that the NNMCWDA method can effectively work out the problem of channel utilization degradation, greatly improve fairness performance, and increase system throughput. On the side, what's particularly nice about this approach is that it requires only minor modifications over 802.11. In multi-rate networks, the minimum competition window is dynamically adjusted in line with the transfer rate. Its physical realization is very simple and handy, and can be achieved only by writing driver programs without any hardware modifications. Therefore, it is easy to execute and popularize in an actual network.