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The ad-hoc network is paid to attention aiming at the achievement of the ubiquitous society. In ad-hoc network, multi-hop communication is used and source node constructs routes to destination. Applications of ad-hoc network are inter-vehicle communication and sensor network and so on. Among them, wireless sensor network is attractive in an emergency such as disasters. In this application, one of the problems is congestion for increasing of traffic of the urgent and medical data packets on wireless communication routes. It is a problem to be solved to guarantee quality of service in ad-hoc network in an emergency. In this paper, we pay attention to congestion and propose the protocol to improve transmission delay for ad-hoc network in an emergency. The main routes (the shortest routes) are constructed by using a proactive routing protocol, OLSR (Optimized Link State Routing), in this paper because of this premise, the network topology is no change and heavy traffic. And, the alternative routes are constructed by using a reactive routing protocol, AODV (Ad hoc On-demand Distance Vector), when a node receive a control packet of congestion acknowledge from congestion node. Therefore, it is avoided to overlap of main routes and reduce delay and packet loss. Additionally, data packets are given priority level and the low priority packet uses the alternative route. As a result, the high priority packet such as the urgent and medical data is transmitted low delay and packet loss. We evaluate transmission delay by congestion to preparing conventional protocol OLSR.