The Implementation of Quality Assurance System is a step for organization in improving their Quality Management System. PT. TPI is a supplier for Multinational Automotive Company, therefore PT. TPI must apply Quality Assurance System to create satisfaction and fulfill customer requirement. Quality management system at PT. TPI has already running but limited on quality control activities and has not covered the quality assurance of suppliers, quality assurance, delivery assurance, and customer acceptance guarantee. The purpose of this study to design a quality assurance system at PT. TPI that can ensure every implementation of activities and all types of work that aims to produce products to be created, received, and will be sent by PT. TPI. This research is qualitative through data collection using interview and field observation at PT. TPI. The analysis is assessed based on Gap Analysis by comparing the situation in PT. TPI with each clause in the Customer Quality Assurance System Requirements. From the result of the average value that is equal to 18.48%, it can be concluded almost all activity of Quality assurance system executed and documented almost totally fulfill the requirement, but there is negligence and inconsistent in its daily control.