The purpose of this study is to know service of service performed by PT Nasmoco Siliwangi Semarang, to know the customer’s is loyalty to PT Nasmoco Siliwangi Semarang, and to determine the influence / relationship between service of service to customer’s loyalty to PT Nasmoco Siliwangi. In this research, a sample of 100 respondents are drawn using incidental sampling and data collection methods in this study used interviews, questionnaires, observation and literature study. Mechanical analysis used examination of the validity, reliability, simple linear regression, statistical test t, and the coefficient of determination using the IBM "SPSS 16.0". Based on the results of simple linear regression analysis it can be shown by the regression equation Y = 4.194 + 0,495X + e, t test t hitung > t tabel ( 3,869 > 1,984 ) significant value 0,000 < 0,05 and determination coefficient was 0.124. This means that 12.4% of service of service to customer loyalty. According to the data analysis it will be known that service of service has a significant impact on customer loyalty. It can be recommended that suggestions for Nasmoco Siliwangi Repair Shop should match between the supply of spare parts in Nasmoco Siliwangi and the warehouse. The company should also adds the stock of spare parts, body kits, and accessories, the officer should give an explanation about the terms and conditions in detail. However, according to time schedule it is approximately2 hours for a standard service the technician should improve customers, is satisfaction continue to provide good service. The customer is loyalty will be created after they feel satisfied with services provided and repairing service to Nasmoco Siliwangi.