The invention discloses a generator excitation system comprising multi-type limiting units. The generator excitation system comprises a low-excitation limiting unit, an over-excitation limiting unit, a PID adjusting unit, a power amplification unit and a stator over-loading limiting unit (including stator over-current limiting and maximum idle limiting). Output of the low-excitation limiting unit can be connected to the input end of a front high ratio door of the PID adjusting unit or the input end of a back high ratio door of the PID adjusting unit or a voltage overlaying point. Output of the over-excitation limiting unit is connected to the input end of a front low ratio door of the PID adjusting unit or the input end of a back low ratio door of the PID adjusting unit. Output of the stator over-loading limiting unit is connected to the input end of the front low ratio door of the PID adjusting unit or the input end of the back low ratio door of the PID adjusting unit or the voltage overlaying point. The over-excitation limiting unit, the low-excitation limiting unit and the stator over-loading limiting unit can meet the requirements for various access modes, simulation testing shows that the established models are stable and reliable in action and accurate in definite value and accord with device actual measurement characteristics, and engineering application requirements are met. In addition, the models can be used as the reference for technical staff of excitation system simulation study.