The focus of this research is on presenting an optimized structural design for prestressed concrete sleeper type B70. In approaching this optimized design, current practices in the design of concrete sleepers, assumptions and design criteria are surveyed and then the sensitivity analysis with SAFE software is made based on 5 criteria. 40 sleepers with different dimensions are put in this analysis. Having chosen the one with the best geometrical condition among those 40 sleepers, the prestressed concrete design method is used for determining the number and the place of rebars. Finally, the designed sleeper is analyzed and a comparison between the proposed sleeper and the current B70 with regard to the structural strength and the construction costs is presented.