Given this background, most studies focused on multiplicative thinking and proportional reasoning but they tended to deal with it respectively. Little is known about how one kind of thinking is related or influenced to another kind of thinking. Given that multiplicative thinking is important and is a foundation for later learning of proportion, it is informative to look into multiplicative thinking in relation to proportional reasoning. Specifically, this paper explores how multiplicative thinking works in solving proportional problems. It first explores students’ multiplicative thinking levels and their characteristics, and then scrutinizes how they may function in solving proportion problems. As such, this paper gives some implications of the importance of multiplicative thinking and instructional directions.