Abstract: Based on the noise channels(both forward and feedback channels) and considering many influencing factors such as random decomposition of packet,sliding window length,packet length and its propagation delay in data link,the models M^X/G/1 on the delay performance of both GBN-ARQ(go-back-N ARQ) and SR-ARQ(selective-repeat ARQ) systems are established under the group arrival of packetes.The formulae to analyze propagation delay and unitary maximum throughput are also deduced for GBN-ARQ and SR-ARQ.For given transmission conditions,the model and method to determine and control the minimum sliding window are obtained too.System simulation shows that if the length of sliding window is changed adaptively,the delay of GBN-ARQ can be reduced and the transmission efficiency can be enhanced; therefore,the complexity to implement SR-ARQ in wireless system can be avoided by substituting GBN-ARQ for SR-ARQ in some conditions.