Effective and efficient navigation and representation of the entire structure of the product catalog is one of the important factors for on-line market. This paper proposes an application using Treemaps visualization to enhance the functionality of online product category. We aim to develop high-quality catalog interfaces in terms of readability, understandability and comprehension by integrating graphics into Treemaps. We applied two types of Treemaps: 1) Slice-and-Dice Treemaps, 2) Squarified Treemaps, into the on-line catalog to address the "small window" problem allowing buyers to overview and navigate large product categories dynamically. We also use a history bar that locates on the top of each category and sub-category to provide a 2.5-dimensional view of contextual information.