More and more business are waking up to the value of their data and starting to realize the values of the data in terms of making profit through enhancing marketing productivity, improving customer relationships and building up competitive advantages. Online retailers collected a lot of customer online shopping data by tracking every transaction instantly and accurately. Those valuable data could help online retailers to gain deeper insights in the aspects of product trends, segmentation of customers and targeted personalized advertisements. With data analysis and business intelligence, we could not only answer questions about how the business performed in the past, but also make predictions and help business make decisions. In this project, we conducted analysis on transactions data of an online shopping website during 2009 and 2011 period. The project answered questions about which products are fast growing and declining, analyzed customer purchase behavior and segmented customers into 4 major clusters, identified how each customer cluster are characterized, and studied products trends of loyal customer cluster.