The purpose of this research was to redesigning the user interface architecture of the digital library website of the National Library and Archives of Iran (NLAI( using card-sorting method in order to improve the structure and the desired retrieval. The present study is an applied research. To this end a multifaceted approach and various techniques such as interviewing, think-aloud protocol and card-sorting were used to redesign the user interface architecture of the digital library website of the NLAI. EXCEL and VISIO software were used to analyze the data, and Sort Optimal tool was used to analyze the data obtained from card-sorting. The results were read in the form of similarity matrix and dendrogram algorithm. The statistical population in this study included users of the digital library website of the NLAI, who were selected in two groups of novice users (clients) and advanced users (librarians). In order to validate the qualitative findings, the researcher triangulation method was used. Findings of the research, the model and the results obtained from Card Sorting test, were provided to 7 experts, researchers and professors of library and information science who had necessary experience, for evaluation to give their expert opinion in the field of data analysis. The similarity matrix findings showed that users grouped elements such as "Ask Us", "Legal Considerations", "Resource Registration", "Resource Donation", and "Technical Support" and so on. The findings of the Standardization Network also confirmed that users have included 10 times "Ask Us", 17 times "Resource Registration" and 6 times "Technical Support" in the menu of electronic services. Dendrogram findings also showed that a number of contributors expect to be able to select "source type" if necessary next to the search box, rather than independently reviewing individual digital resources. Cart sorting process analysis showed that in addition to predefined categories, some new categories were suggested. These included "links to other digital libraries", "shared databases" and the "FAQ" category. The data and performance of users in this study showed that the current user interface of the digital library website is not user-friendly and users cannot quickly get what they are looking for. The card-sorting process generally acknowledged inconsistencies in how users perceived the labeling and organization of digital library website content. Interviews and think-aloud protocols with users also confirmed that the language used to name menues and information elements is currently not simple and user-friendly. User categories in the card-sorting process for designing the user interface architecture also showed that there are elements in the website that users do not need, and conversely, there are important elements that are not included in the website. In the simulated information architecture, based on the findings of the interview and the participation of users in the Card Sorting process, an attempt was made to design the proposed user interface somewhat similar to other user interfaces (OPAC and Rasa software). In the proposed model, while paying attention to the demands and expectations of users, the simplicity of the pages, the most important point has been observed.