This paper proposes an analytical model for delayed reservation scheme, which can be exactly analyzed. By applying it to a server-based QoS management network, we can obtain the related blocking probability and the waiting time distribution of requests, and discuss its performance by means of numerical results. The numerical results show that the delayed scheme can improve the blocking probability by about two order of magnitude compared with the conventional reservation scheme even when a small acceptable waiting time (e.g. 20% of average flow duration). We can conclude that the delayed reservation scheme can lead to significant improvement in a server-based QoS management network performance.