Recently, with the development of wireless communication technology and the widespread use of mobile devices, location information has been used in various systems and services, such as the global positioning system (GPS), other positioning methods are used for outdoor positioning, including the use of received signal strength indicator (RSSI) between communication devices. The RSSI-based positioning method has lower positioning accuracy than GPS, but it has advantages such as low cost and power saving. The RSSI-based positioning system calculates the distance from the RSSI between the target and the router, which is used to measure the RSSI in this research and uses some algorithms to determine the position. However, in actual positioning, there are often fading and multipath propagation due to the ground, people, and other factors. When an RSSI is used in positioning, the accuracy of positioning is often greatly reduced. Therefore, reliability is introduced to increase the accuracy of the estimation. In this research, based on the above background, this research proposes a method to improve positioning accuracy by determining the reliability of routers and selecting reliable routers to perform positioning. Furthermore, real data will be used to compare with other methodologies.