Abstract One of the most important goals moving toward banks customer satisfaction is reducing waiting time in branches. Banks are queuing system including that long queues of customers will cause Increase customer waiting time and decrease satisfaction. One of the effective solution for reducing waiting time is optimizing number of service personnel in each sector which in addition to reduce the waiting time, it has increases employee engagement. In this paper, simulation and experimental design method has been applied to this topic. This paper is developing a model with two objectives; Minimizing customer wait times and maximizing working time of employees. First, the current status of MELLI bank branches is simulated by ED, then Improvement scenarios is implemented by DOE methods and finally model is solved by design-expert software. The results show that most favorable option is one electronic and clear employee and five Cashiers employees. Using this method resulted in reduced waiting time by 32 percent.