The Rankine cycle is one example of vapor power cycles. One important application of it is in steam power plants. In this paper, a simple model of the steam power plant is designed to study the effect of increasing boiler's pressures (3, 4, 5, and 6 bar respectively) on the efficiency and the dryness friction of the Model. Properties of the important points in the cycle were calculated consequently the losses in the pump, the losses in the condenser, expansion of the working fluid through the turbine, and the heat transfer to the working fluid through the boiler were determined. From the results, it was found that with the increasing of the boiler's operating pressure the thermal efficiency of the model cycle increases due to a substantial increase in network. Thus net-effect is marked increases in the thermal efficiency of the cycle on account of these measures.