Abstract: There are intrinsic differences among workers in production system. Workers have different experience, knowledge, and different rates of learningforgetting, which greatly affects the performance of a production system. In this paper, in considering workers’ learningforgetting, a mathematical model of workeroperation assignment to achieve a minimum cycle time is presented. By this model, a steady state workeroperation assignment solution can be obtained with the workers’ professionals. Based on the model, simulations are performed under given particular production environment for heterogeneous workers for specific objectives. It shows that good results can be obtained by using the proposed method.