The purpose of this study is to examine whether the key concepts and major relationships presented in the textbooks are systematically well-learned by students. The conceptual networks representing middle school science textbook content and 5 students’ cognitive structure on the plant nutrition and photosynthesis were analyzed by concept network analysis. The results showed that there are many concepts and relations used in the textbook so almost all students can’t learn them all. And the contents of structure and function integrated relations about plant nutrition which set in the national curriculum were included in the textbook, but not in the students’ conceptual network. Also, the structure and composition of concept network showed different characteristics among students according to academic achievement. Thus it is necessary to check whether the content covered by the school level is structured with appropriate linkage and differentiation considering the developmental level of the students. And teachers should provide a continuous explanation of the overall structure and the functional relationships when teaching photosynthesis to students.