Generation unit power fluctuation frequently occurs in the generation scheduling model which aims at minimizing the generation costs. To solve this problem， the unit power fluctuation penalty factor is introduced. Based on the different characteristics of units of different capacities， a unit power fluctuation linear penalty model and a piecewise penalty model are developed. An actual provincial power system is used to examine the developed models. The results show that the models can reduce the fluctuation of large and medium-size units and make the output power smoother. The model can improve output characteristics of the small capacity units， making it easier to operate. The models also satisfy the limit values of network security constraints.