Since Taiwan High Speed Rail joins the market, different transportation companies depending on their business characteristics have their own strengths and weaknesses. Besides, the passengers have a wide variety of choices in transportation. Therefore, service quality and satisfaction are essentially important. For this reason, the research mainly lies in applying importance-performance analysis to identify the major strength and weakness service quality attributes of passengers' perception based on SERVQUAL model with 26 items. The results show that ”Their physical facilities are visually bright and tidy” and ”Their employees are always willing to help customers” are the most important attributes to customers. Three attributes with high importance but low performance are required for immediate improvement, i.e., ”The company performs its service accurately”, ”Employees have adequate knowledge to do their jobs well”, and ”The ticket price can be differentiated by different groups of customers”.