Recently, in Global competitive environment, each enterprise needs to maintain their competitive advantage to get success. Customer satisfaction is one of the most important factor to help them to do this. Customer satisfaction and service quality are inter-related. Viettel IDC is one of the biggest IDC service providers in Vietnam and they also intend to improve service quality and customer satisfaction related to colocation service. The purpose of this research major focuses on how to define which factors are impact the customer satisfaction of Viettel Colocation service and then make suggestion to improve them to maintain competitive advantage of Viettel in Vietnam’s IDC market. In order to determine the satisfaction factor and levels of Viettel colocation service, the author have done the quantitative methodology to evaluate the current relationship between the customer satisfaction and service quality measurement, the object is customer (included both personal, enterprise, SMB and finance, government…customer) who have been using Viettel IDC service. The author had gathered primary data in the form of conducted survey questionnaires. The author has already relied on secondary data resources from book, other related researches, and articles for research. From those data, the author did the data processing by SPSS software, taken analytic and conclusions on the current status, based on those, given some suggestion and recommendations to the manager of Viettel IDC to help them improve colocation quality service to get better customer satisfaction levels.