XYZ is a Small and Medium Enterprise (SME) that manufactures dolls from rasfur and velboa fabrics. XYZ uses a flowshop with a make-to-stock production system. The problem that occurs in XYZ is that they have not been able to achieve production targets so they cannot complete customer demands. This study aims to simulate the production system so that it can be analyzed problems and taking the best solution. The method used in this study is modeling and simulation using flexsim 6.0 software. After modeled on Flexsim, it can be seen that significant problems exist in the flow from cutting to the sewing machine and the sewing process time is too long. Therefore, the researcher tries to add a sewing machine as an investment so that there are no lost opportunities. After the addition, it turned out that XYZ was able to produce an average of 80 dolls per day by adding 2 sewing machines as a future investment.