In the rapid product design and development, design rationale (DR) information is critical for designers to understand the design technology and for better knowledge reuse. The visualization of DR capture, search and retrieval systems is important in assisting designers to gain insights and benefits from the increasing DR repository, e.g. major design issues of an artifact and design alternatives to the issues. In literatures, we have observed that the current DR systems provide limited interactive guidance in helping designers to DR navigate and search. In our previous work, we have proposed an ISAL (Issue, Solution and Artifact Layer) model for DR discovery in which the DR information is mined from a large amount of archival documents using text mining techniques. In this paper, we focus on interactive user interface (UI) design for our DR retrieval system. With functions like view, search and analysis, designers are visually guided during DR searching. Using patents as our research data, the view functions enable engineering designers to intuitively navigate DR repository. Search functions support designers to retrieve relevant DR from multiple aspects and visualize the structure of relevant DRs from a holistic view. By applying analysis functions on the retrieved DR, visualization is able to suggest some useful DR insights, e.g. key components of certain issues, possible solutions of relevant issues, major issues of an artifact and technology development trend analysis, etc. Together with the function examples, we illustrate the merits of our interface design for DR search and retrieval.