To ensure that the key indicators for conformance of the UHF RFID tags on the packaging of items comply with relevant standards and address the issue of incomplete description of key indicators in existing literature, the work aims to study the testing methods of the key indicators for conformance based on ISO/IEC 18000-63 and ISO/IEC 18047-63. Based on the research and explanation of existing conformance testing methods, the testing methods for state transition and truncated response were improved, enhancing the accuracy of testing. A testing method for slot counter was designed, which verified that the slot counter responded only once during the non-zero to zero change process by changing the Q value and repeatedly sending the QueryRep command, thus avoiding the phenomenon of multiple tags responding simultaneously. By the improved testing method, the designated tags were tested and the test results met the standards. This study achieves more comprehensive objective verification and effective evaluation of RFID tags, which is of great significance for improving the reliability of RFID tags in practical applications.