A 1 MW organic rankine cycle（ORC） system was designed based on the self- developed software. Considering the characteristics of ORC system, design of axial turbine with organic medium, which was suitable for this system, was introduced. Comparative analysis of different types of expander ＇s characteristics in ORC system, such as radial inflow turbine, screw expander, and axial turbine, was made. Advantages of the application of axial flow turbine to the ORC system were summarized. At the end, a 1 MW axial turbine using refrigerant R123 as working medium was designed. Optimization and structure design of flow passage were done using CFD numerical simulation.