In the paper, we propose the I-S model to conduct research on the service quality of a library from the customer demand prospective. The data for model test includes the effective questionnaire of 431 by personal survey in Minghsin University of Science and technology. The software SPSS 15.0 is employed for data analysis and calibration. The results indicate the statistical significance that the service quality of tangible, reliability and assurance do not meet the customer expect, which directly impact the customer satisfaction and reuse intention. This study would provide a beneficial reference for the management in improving the service quality of a library.