The Korean Decimal Classification (KDC) and Nippon Decimal Classification (NDC) are national classification systems of Korea and Japan. They have been used widely in many libraries of each country and maintained successfully by each national library associations of Korean Library Association (KLA) and Japan Library Association (JLA). This study compares the general characteristics of these two national classification systems using their latest editions of KDC 6 and NDC 10. After reviewing the former research, their origins, general history and development, and usages were briefly compared. Various aspects including classification by discipline, not by subjects, decimal expansion of the classes using pure notations of Arabic, hierarchical structure, and mnemonics quality are checked for both systems. Results of the comparative analyses of major auxiliary tables, main classes and 100 divisions of schedules of two systems are suggested one by one with special regards to Dewey Decimal Classification (DDC). The analyses focus on the differences between both systems as well as the characteristics which reflect the local situations of both countries. It suggests some ideas for future developments and research based on the results of their strengths and weaknesses.