UPH library website is one of the students’ learning media. Therefore, the design and content of the website should facilitate students in using it. The ease of use can be measured by conducting a usability test so that the problems which students faced when using the website and find the solution for improvement. The usability test will be done by using WEBUSE and experiment. Questionnaire is used to gather students’ opinion about website library’s usability level. Based on data taken, it is known that website library’s usability level for category Content, organization and readability; Navigation and links; and Performance and Effectiveness are considered to be at moderate level with each usability point respectively 0,598; 0,593 and 0,576. For user interface category, it is considered to be at good level (0,640). From result of correlation test, it can be inferred that there is no relation among the usability’s categories. Therefore, each category should be improved specifically. Experiment is performed to identify usability problem directly by observing respondent while doing their given assignments. According to the results, respondents still find difficulties when using UPH library’s website. This can be inferred from average learnability point is 51,67%, low effectiveness (differ 21 -79 seconds with expert time) and low efficiency (differ 1 – 4 click to expert click). Several usability problems that have been found are search menu does not work well, important information is written too small and some menu’s names are not familiar or do not represent the menus’ content.