The traditional adaptive modulation and coding(AMC) have to choose transmission rate adaptively only according to channel state.In order to achieve better performance of the network,an improved AMC considering both the channel state of the physical layer and the buffer queue length of the data link layer is proposed,that can choose the transmission rate self-adaptively according to the buffer queue length of the link layer and the channel state.Compared to the traditional AMC method,this improved AMC can ac...