This study aims for developing an instructional design strategy to improve collaborative teaching between teacher librarians and subject teachers in library-assisted instruction. Collaborative teaching is an important management activity enhancing teaching role of teacher librarians in their school community. But in the actual condition the level of the library-assisted instruction as its practical strategy is cooperation and subject teachers are leading teaching and learning except for selecting resources. Because library-assisted instruction is resource-based learning, the procedural knowledge of information literacy curricula and topics of subject specific curricula should be designed as a whole. Also, there must be possibilities of reducing trial and error and expanding successes. From these sides, the collaborative design strategy for library-assisted instruction can be planned like 'statement of learning situation-co designing-co teaching-co evaluating'.