The unit single capactity of the horizontal hydraulic turbine-generator unit exported to Vietnam has the rated power of 6 750 kW and rated speed of 1 000 r/min, which has the characteristic of large unit single capacity and high rotation speed, etc.After briefly introducing the structure characteristics of the rotor part, the methods of establishing Pro/E model and analyzing finite element were presented through the example of stress analysis of generator rotor cross section under condition of rated and runaway speed, and the computed results were analyzed and summarized. In the analysis process, the Pro/E modeling integrated with ANSYS simulation was realized, model establishment and finite element analysis were finished by the software. The results show that the structures of main shaft and magnetic poles reach the design requirements. Compared with the traditional calculation method, its precision can better satisfy the engineering demand, and the efficiency is highed.