This study explored the possibility of service robot in assisting children's book locating activities in libraries. A comprehensive review of children's experiences of library resources locating was made to develop the library robot and the corresponding criteria for evaluation. With a working prototype of library robot, this study examined effective and appropriate interface and information design to assist children in book locating activities by empirically collecting their performance and perception with robotic assistance in a genuine library setting. The result suggested that robot guidance effectively led children to find the assigned book in library while received high appraisal in its efficiency in guiding children to find the book. Children participants regarded the library robot as a favorable and friendly agent to provide interesting navigation experience in the library.