This thesis offers useful information for developing and restructuring Korean textbooks by analyzing organizing systems of writing-related units. For the analysis, 52 small units from 12 high school Korean textbooks based on the 2015 curriculum reform were collected and analyzed in terms of unit construction and learning activity. The detailed criteria used for the evaluation of unit construction were mechanism, forms, and importance of integration between different domains, writing genre, and features of main materials, while the criteria for learning activity were completion of writing, separate guide for activities, use of collaborative writing and various media, and types of activities. Results were discussed to offer some proposals for future textbook development.