The stator winding-to-ground capacitor is an important parameter of generator, and its accurate measurement can provide important basis for the stator grounding protection scheme. On the background, the fault branch of generator stator winding is divided, and the internal structure of voltage transformer is studied. Then, a real-time measurement method for the stator winding to ground of generator based on the injected current signal is proposed. Firstly, the current signal is injected from the low-voltage triangle side of voltage transformer for the generator and flows through the high-voltage side of the voltage transformer and the capacitance of the winding to ground. Secondly, the low-voltage triangle-side voltage and the low-voltage star-side voltage of the voltage transformer is measured respectively. The simplified circuit and the injected current signal and the measured voltage signal calculate the stator winding capacitance to ground. This method avoids the influence of the short-circuit impedance of voltage transformer on the measurement results. The PSCAD/EMTDC simulation and experimental results show that the measurement method is safe in process, simple in wiring, and accurate in results.