As the digital revolution continues and the use of the Internet further develops, digital libraries have become an important tool for communication and development of digital culture during the Internet era. Digital libraries will also play a more important role in the future development of digital culture and society. Searching for both printed books and E-books is now frequently done through a digital library interface. This is important when considering the development of digital media and mobile devices. People will have a preference for how they interact with a mobile device to search a digital library. How do people search for books? What is required in a digital library interface on a mobile device? Do people have a preference for how they search for books on a mobile device? What are the factors that affect people's preferences for library search interfaces on a mobile device? These are the main issues that need to be explained and studied in this thesis. The features of a digital library interface on a mobile device can affect people's preferences. There are nine features that could help to improve library search interface design, which involves book title, author, publisher, time, little book cover, bigger book cover, introduction, location, and price. This research concerns on assessment of people’s display preferences for digital library interfaces on a mobile device. The researcher investigates examples of different library search interfaces to assess people’s display preferences for a library search interface on a mobile device. By analyzing and discussing the results of this research, the researcher investigates the factors that affect people's preferences for library search interfaces on a mobile device. This thesis shows different preferences of readers for different library search interfaces. The conclusion is that people who participated prefer different factors of the digital library search interfaces on a mobile device. People with different backgrounds tend to prefer the traditional library search interface with book title, author, publisher, time, and little book cover. This trend is not affected by the order of examples of different library search interfaces.