Recently relationship marketing is fully utilized in service industry. It is hard to measure the quality of service, but Berry (1993) indicted that relationship marketing can overcome invisibility of service. However, for heavy duty mechanic service industry, there are little studies about that. Therefore, this research utilizes Discriminate Analyses to analysis factors of customer loyalty and utilizes Structural Equation Modeling (SEM) to build up the cause effect model of relationship marketing, relationship quality and loyalty. Besides, this research also utilize Factor Analysis to exploit potential variables of relationship marketing, analyze the association between relationship marketing, relationship quality and customer loyalty and evaluate the direct and indirect effect of relationship marketing toward relationship quality and loyalty. According to this research result, first, for customers the most valuable activity is customer oriented among all the relationship marketing activities. Second, the order of relationship marketing factors which affect customer loyalty is customer oriented, professional technique and afterward service. Third, the order of factors which affect the relationship quality of customer loyalty is satisfactory, promise and trust.
