The purpose of this study was to explore the aspect of meaning construction on writing from sources in the elementary school 5th grade class. In order to accomplish this, I made the students write after reading source texts which are related to writing task. I examined reading strategies and aspect of knowledge-transforming on writing from sources. This study focused on searching the reading strategies and aspect of knowledge-transforming on writing from sources rather than generalizing it. Based on the results of the research, there are differences in using the strategies and transforming the knowledge between high-level writer and low-level writer. Therefore, we need to educate writing from sources in the elementary school. I expect to examine writing from sources focused on elementary students.