In recent, blended learning which combines classroom learning with e-Learning is getting more and more attentions and expectations. However, there are little research efforts on blended learning, especially on blending guidelines for blended learning. Even the training institutes which already implemented blended learning had started it without any directions and guidelines. The purpose of this exploratory study was to develop a blending guidelines for blended learning based on the literature and the results of case study on blended learning. To implement the blended learning, the factors of students, teachers, contents, instructional strategies and developmental circumstances are considered. Factors of students contained the level of informational development, favor of e-Learning, the size of class, motivation. Factors of teachers contained the level of informational development and favor of e-Learning. Factors of contents contained the type of knowledge and the changable cycle and factors of instructional strategy contained the needs of synchronized feedback, learning strategies. finally, factors of developmental circumstances contained the duration and the expenses of developments for learning materials.