At the time of disaster, the use of MANET is expected as an alternative communication method when the existing cellular phone communication network cannot be used due to the collapse of the base station. Usual MANET routing protocols are designed on the premise that the IP address of the destination node is known. Therefore, for example, when a victim requests relief in the case of a disaster, communication cannot be performed unless the IP address of the node of the rescue team is known. In order to solve this problem, we have proposed AODV-SOS and FORP-SOS which implemented SOS packet without destination address in MANET routing protocol AODV and FORP, and evaluated their communication performances. In this paper, in order to improve the performance of FORP-SOS, we propose a method to discard SOS packets if the received signal strength is less than a preset threshold when each node receives an SOS packet. We implement the proposed method on a network simulator and evaluate its effectiveness.