Abstract: By software application in large state-owned enterprise, it was found that some rare used Chinese characters could not be displayed. In this text, the problem was comprehensively analyzed from aspects of tool development, system configuration, data base connection and so on. The solution was to upgrade Oracle database character set. The method of upgrading database character set was comprehensively tested to confirm the solution and check it in practice, which provided good practical experience in cross-character set upgrade of enterprise-level Oracle database.