Abstract: A 300 MW pumped-storage electric generator motor is taken as the model to study the design of large pumped-storage electric generator motor and the simulation of related parameters. Matlab software was used to calculate the magnetic circuit, and then verification and modification were performed to reduce the error. The finite element simulation was carried out for the generator, and the air gap magnetic density distribution cloud diagram was observed to analyze its magnetic density and load condition. The parameters such as voltage, current and air-gap magnetic density were simulated and compared with the calculated results to verify their correctness. By changing the length of the air gap, the length of the core and the pitch of the damping strip, the magnetic flux density, the core loss and the eddy current loss of the damping strip under different lengths were compared and analyzed.