When laying intensive tags, there is a coupling between the UHF RFID tags. It causes the system performance degradation. If the power one tag received from reader is less than the activation power of coupling tags, or the reader can’t receive the reflected signal of coupling tags, then the reader can’t be normal communication with the coupling tags. Firstly, in this paper, the performance of the forward link and the reverse link theoretically derived from the coupling tags. And this paper also simulated the gain and scattering area when many tags are put together. Then the ratio of the maximum reading distance of forward and reverse link analysis and figures out RFID restricted link. Finally, the experiment of antenna probe proves this thesis conclusion. The conclusion for the reader antenna selection, proper placement position of tags and improve RFID tag read performance system is of great significance.