Nowadays, with the advance of communication & information technology, the need for globalization and localization on subjects is paid more attention. The localization depends much on the propagation environment. Especially, in the indoor environment - complex environment, the direction of radio wave is hardly predictable. If the authors know effects of propagation environment, the authors are able to calculate and estimate the position of objects in the effective average area of RF signal. Hence, this paper is going to present an overview of some factors that limit the performance range of indoor passive RFID positioning systems. Received information of passive reference tags are used to predict approximately transmission losses along the transmission distance. Then, the two - dimensional localization of objects in the indoor environment is presented into details. the system is built with the improved Landmark model: using the passive RFID tags, using only one reader antenna, designing system in a small experimental room with many moving people and electronic devices around.