The purpose of this study is to investigate the process of students' construction of scientific explanations through drawing explanatory diagrams. For this, we observed fifth and sixth graders' drawing processes in a gifted science class involving learning physics concepts in mechanics. The analysis was carried out on three pictorial representational levels: sensory (e.g. observed materials), unseen substance (e.g. molecules) and unseen non-substance (e.g. forces). We found that there were five patterns of interplay depending on the sequential path through the pictorial representational levels. All students began drawing explanatory diagrams from the sensory level as the first step and then constructed explanations using the unseen levels based on the interplay among different levels. In the process of forming meaningful relationships among the three levels of representation, students focused on a specific phenomenon through drawing at a sensory level and extended their making sense of the phenomenon from what happened to why it happened. Based on these findings, we suggest how teachers can use the interplay among the different pictorial representational levels to guide students in generating scientific explanations through drawing.