The main purpose of this study is providing a national curriculum adaptation model for multi-grade classrooms. For this purpose, a large mass of related literature and some countries experiences on multi-grade education have been reviewed and analyzed. Furthermore, on the basis of the document analysis and conducting interviews with domestic and outsider experts the conceptual model of multi-grade curriculum model has developed. The designed model has been validated by 15 experts of curriculum and instruction experts (PhD faculty members). The first draft of introduced model to the experts has been modified on the basis of their comments. The validated model has 10 components that will be described in the article.