P T. Akebono Brake Astra Indonesia is a company engaged in the manufacturing industry that produces motor vehicle components. The company's product type is Make To Order where the company carries out a production process on an automatic assembly line to fulfill orders from consumers. The product studied was the Master Cylinder. The problem faced is that the company wants to design a combined Master Cylinder assembly cell. The combined design of cells is needed because there is one assembly cell that has order. This assembly cell produces export quality products that have erratic orders. Based on the current condition, a research aimed to design a combined assembly cell for Master Cylinder products using the Group Technology approach with the machine approach principle and the similarity principle then visualizing the simulation results to evaluate the performance of the combined assembly cells. The research stages began with the analysis of the actual condition of the assembly cells in the form of output per day, working hours, and the division of labor between types of products. After that, data was collected in the form of product variations, cycle time, production output, and cell assembly capacity. This data serves to provide input in proposing a new assembly cell design using the Rank Order Clustering and Similarity Coefficient methods. The stages of the ROC method are to assign binary weights to the machine-variation matrix of products, then provide a decimal equivalent value and provide a ranking until there is no change between rows and columns. The SC method is to create a machine-variation product matrix then calculate the similarity coefficient value between rows of columns, then determine the key machine to perform matrix grouping until a machine group is obtained. After obtaining the classification of the machines from the two methods, and efficiency analysis was carried out using Performance Measure. After that, visualization and evaluation of the cell design is carried out by creating a simulation model. Based on the results of the GT design, cells starting from 4 cells become 3 cells. The output is 140 pcs / hour, efficiency is 90% and the working hours are 19 hours. The simulation results in the selected proposed model are to reduce the assembly cells with a simulation time of 409.30 hours. When compared with the initial simulation time of 479.65 hours, the proposed improvement can minimize the time by 70.35 hours.