For indoor location, an active RFID indoor location system is designed. The system is designed and implemented by using a RSSI-based ranging technology location algorithm. In this article, the author amended the RSSI ranging equation, proposed and implemented a way to extract and estimate the environmental parameters of specific application scenarios, and improved the accuracy of the RSSI ranging. After many statistical experiments, the results show that the system’s deviation can reach 10cm on the diagonal of the region, and about 30cm on the edge. Through statistical calculation, the average deviation of system position is about 10.6cm, which is a good location system of high precision. When implemented for different applications, this system has the advantages of simplicity and adaptability.