Radio frequency identification (RFID) technologies as an effective indoor localization solution are acquiring increasing attention for its low cost and compactness and it plays a significant role in industrial engineering. However, the location accuracy strongly relies on environment factor that will affect the signal propagation property (using by position system). To alleviate limitation imposed by this reason unlike others, this paper proposes a new calibrated Received Signal Strength Indication (RSSI) propagation curve for high accuracy under metal noise factor. Therefore this curve is obtained by taking the metallic effect characteristic into consideration. The proposed results are obtained from practical experiments by RF Code M250 and R150 tags. Aimed at incorporating these features into localization algorithm appropriately and then the accuracy of RFDD-based positioning system under metal noise factor can be improved substantially.