The invention discloses an electric generator minimum exciting current limiting method. Currently, electric generator minimum exciting current is limited by means of a fixed threshold value method; according to static stability analysis of an electric generator during operation, the electric generator allows the minimum value of exciting current to be relevant to the electric generator, power grid parameters and operation conditions. A minimum exciting current limiting method with a fixed threshold value cannot be adaptive to changes of the operation conditions of the electric generator, or cannot guarantee safe operation of the electric generator in full ranges. According to the electric generator minimum exciting current limiting method, by means of characteristic analysis of electric generator static stability limit, minimum exciting current allowable values under different work conditions of the electric generator are obtained according to the type of the electric generator, electric parameters and power grid parameters; on the basis of the minimum exciting current allowable values, minimum exciting current limiting threshold values under different work conditions of the electric generator are set and designed, the condition that exciting current of the electric generator is not less than the minimum exciting current limiting threshold values is guaranteed by means of a closed-loop regulation method, the purpose of comprehensively preventing step-out of the electric generator is achieved, and safe and reliable operation levels of devices such as the electric generator and the excitation system are increased.