In this thesis entitled "Thermodynamic analysis of a ship's steam turbine plant", a thermodynamic analysis was carried out for three modes of operation of a ship's steam turbine power plant. The default three modes of operation differ in the rotation speeds of the ship's propulsor, which are 56,65 1/min, 71,03 1/min and 83 1/min. The paper contains theoretical part and the previously mentioned analysis. The theoretical part of the thesis describes the steam turbine plant and its main components, for which a thermodynamic analysis was performed. For each of the components, the role, the principle of operation and the listed divisions are explained. Also, for each component, it is stated in what quantity it appears in the plant and what kind of component it is. In the practical part of the work, a thermodynamic analysis was performed for each of the main components for all three modes of operation. The energies and exergies of all components and the power of certain components were calculated. Based on the calculation results, graphs were made in which the results of the three operating modes were compared. Based on the obtained results of the thermodynamic analysis, adequate conclusions were given, and it is evident that the energy and exergy efficiencies and energy and exergy losses are the highest in the third mode of operation.