The purpose of this study is to compare and analyze the student assessment system of the Korea National Open University(KNOU) and Open University of United Kingdom(OUUK) in the special aspect of its historical origin and development. As an new model of the higher education, ‘open university’ had been appeared itself in the early 1970s. KNOU and UKOU, both of which now have about 200,000 students, have made a significant contribution to the widening of the higher education in each country. As an open university, which has very different nature from the ordinary traditional university, KNOU and UKOU had an important challenge from its beginning, that is, to harmonize or equipoise two core norms, i.e., the ‘openness’ and the ‘universitiness’. As the idea of ‘openness’ was regarded as the incompatible one with the idea of ‘universitiness’ implied in the idea of the traditional university, so the ‘universitiness’ couldn't be harmonized with the idea of ‘university for everyone’. These two core ‘norms’, which constitute the identity of the open university, had sharply and furiously conflicted at the foundation period of UKOU. In the case of KNOU, there was not such an apparent conflict at its beginning. But the analysis of making of assessment system of it shows that these norms have actively worked too. In this study, the qualities of the student assessment policy of the KNOU and UKOU were compared and analyzed from the respect of its historical origin and development. In the context of open and mega-university as KNOU and UKOU, student assessment policy has actually the most important role in the quality management and enhancement. The current qualities of two universities can be more fully understood when they are regarded as the result of the university's struggle with the above challenge.