P T. Mitsubishi Krama Yudha Motors and Manufacturing 1 (PT. MKM 1) is a manufacturing company that produces auto body components. This research observes Colt Diesel (TD) front door l&r. The research is made with concerning on TD front door process production in C welding line. After observing these stages, it is found that the process on the TD door after hemming workstation has the longest cycle time compared to the other workstations. The Problem on TD door after hemming is the quantity of the process more than another workstation, but the process only using one operator, so it can cause the occurrence of bottleneck and affect the production output of TD front door. TD door after hemming is divided into some working elements, from here we could know one which has the longest cycle time is spot welding process. Additionally there is difficulty for the operator to reach the point to be welded and to rotate the jig while the operator spot welds the TD front door. To overcome some of the problems, we design an automated system on spot welding process in order to improve the effectiveness and efficiency both in terms of production output in the process and processing time, as well as to make the operator's work easier. Designing system starts with identify the need for the system. This phase continues until it obtained the chosen automated system proposal concept. As the result, PLC is used as the controller, pneumatic as the actuator and LVDT as the sensor. By then we do the proposal working system design which consists of the planning process, the design of spot gun, support system facility that includes jig and panel, guide and movement design. In designing the movement, we decide the sequence of welding points, the calculation of distance and time that required on spot welding process. From the analysis, we can see the comparison between the current system with the proposed system. Spot welding process time is decreasing from 118.67 seconds to 53.69 seconds, with a percentage of 52.67%. Meanwhile, for a total time in TD door after hemming is decreasing from 297.58 to 186.46 seconds, with a percentage of 37.34%. According to this proposed system processing time, the production output can be calculated on the TD door after hemming from 12 units/hour to 19 units/hour with a percentage increase of 36.84%.