Abstract: The cross-layer adaptive problem for OFDM systems is researched. In order to overcome the problem that the present resource allocation algorithms do not consider frequency efficiency, impartiality and QoS simultaneously, a cross-layer adaptive algorithm based on the minimal mean delay time is proposed in this paper, which considers Channel State Information(CSI) and queue information simultaneously. The algorithm uses the utility theory in economics, and considers the mean delay time as optimal quantity to ensure QoS for different services. The algorithm also uses utility function to ensure the impartiality of different delay times and QoS. The simulation results show that the delay time of the proposed algorithm is slightly better than that of LWDF, and is very better than these of PF and EXP. Moreover, it can ensure the impartiality of delay time, and is applicable to the communications those are sensitive to delay time.