The development of mobile technology enables information access and retrieving to be even faster and more convenient. The more the information needs become diversified, the more effort the University Library pursues to keep pace with the new trends. With an aim to realize how undergraduates use mobile device and what mobile services they are expecting from libraries, this paper, a case study of National Taiwan Normal University, investigates undergraduates' cognition and their demands toward mobile services by a questionnaire survey. The result shows most respondents are using laptops as a major mobile device. ”Personalized services” and ”library collection search” are two items that most frequently utilized. In addition, the price always serves as a critical factor in appealing students to apply mobile services.