This paper discusses optimizing ballast tamping and renewal (T&R) jointly to reduce the life-cycle cost of ballast. A life-cycle cost model is developed to incorporate a track deterioration model and a tamping model. Based on the models, three optimal policies of ballast T&R are investigated, which include fixed intervention level, constant interval of tamping, and optimal nonconstant intervals of tamping. Three algorithms are presented to obtain the optimal solutions for the three policies. An example is presented to illustrate model performance. From a whole life point of view, eight options based on the three policies are compared for a better understanding of the effectiveness of the policies. The results show that considerable benefit could be achieved by considering ballast tamping and renewal together and implementing the optimal policy.