The invention provides a flexible and extensible excitation control system. The excitation control system comprises a signal measurement unit, a self-parallel excitation adjustment unit, a limiting unit and an analysis and decision-making unit. The signal measurement unit sends collected operation information of a generator to the self-parallel excitation unit and the limiting unit at the same time, and after being modulated, compared and processed by the self-parallel excitation unit and the limiting unit, the operation information is sent to the analysis and decision-making unit for analysis. The flexible and extensible excitation control system basically integrates the extended functions of excitation control systems of main domestic generator sets and can be used for analyzing stability of the system after actions such as overexcitation, low excitation and stator current limiting of a limiter are conducted.