Statistics Korea has been diagnosis national statistics every year since 2006. They diagnosis over 200 kinds of national statistics. They have 7 quality dimension used for quality diagnosis. That is relevance, accuracy, Timeliness, Comparability, Coherence, Accessibility. Since we are interest in how well they produce national statistics, comparability has become the most important dimension recently. In this reason, Statistics Korea try to rating quality level and development comparability index for national statistics. This paper propose the practical method of grading the quality level and developing the comparability index of the national statistics.