On the basis of analyzing the problem of unicasting QoS routing in Ad Hoc networks, a new distributed QoS routing algorithm in the Ad Hoc network—EBLLD (entropy-based long-life distributed QoS routing) algorithm, is proposed. The key idea of EBLLD algorithm is to construct the new metric-entropy and select the long-life path with the help of entropy metric to reduce the number of route reconstruction so as to provide QoS guarantee in the Ad Hoc network whose topology changes continuously. The EBLLD algorithm uses the local multicast mechanism, orders and sorts the outgoing link with the heuristic function and entropy metric to reduce the message overhead. The simulation shows that the EBLLD algorithm can acquire a higher routing success ratio with the low message overhead. In addition, the EBLLD algorithm is scalable and applicable to large-scale Ad Hoc network.