In wireless networks, packet access is a popular mode and the key problem is how to improve throughput and access delay performance under limited frequency resource. Based on an existence model, this paper proposes a dynamic parameter protocol model based on packet CSMA/CD and gives out the theoretical analysis and simulation results that are compared with a model in existence. The comparison shows an improvement of throughput and access delay performance, specially the throughput for wireless channel, and these results could be reference to not only wireless channel but also common MAC protocol.