This paper analyzes the electromagnetic torque characteristics of generator before and after static air-gap eccentricity fault via theoretical deduction, simulating calculation,and experiment verification.First,the electromagnetic torque expressions under normal condition and air-gap eccentricity are deduced respectively. Then, the numerical calculation and finite element simulation are carried out on the MJF-30-6 fault simulating generator in Matlab Ansoft respectively. The results obtained from the calculation and simulations are generally in accordance with those of the practical experiments. It shows that the static air-gap eccentricity brings fluctuation whose frequency is twice of the fundamental value, and increases the mean value of the electromagnetic torque by a tiny amount. As the static air-gap eccentricity develops, the fluctuation intensity and increase of the mean value are greater. These findings can offer more convenience for the monitoring and control of this type of fault.