The Radio Frequency Identification (RFID) localizations systems are actually from the most used in indoor environment. But this kind of closed environment allays presents more perturbation due to walls, roofs, obstacle presence and generally affect the measurements especially sensible parameters like the signal phase which can provide precious additional information for a better accuracy. In this work, we propose an alternative to resolve this problem; we propose a phase cleansing algorithms based on Received Signal Strength Indicator (RSSI) selection. Our proposition consists to select just the phases corresponding to the best reads based on RSSI. Then, we use the selected phases as a metric for localization without using RSSI. We test our proposed approach on an RFID localization system composed from a set of EPC global Class-1 Gen-2 UHF RFID tags, an UHF RFID reader using a 7dbi antenna and a computer for data acquisition and processing. The system is carried by an operator and measurement zone was placed on a wall of 5.5m×1.25m.