For the generators of old small hydropower stations in Xinjiang, the dual winding reactance shunt self excitation constant voltage system is commonly used, which is prone to oscillation, demagnetization and even out of step disconnection during grid connected operation. For these problems, a new excitation method with simple transformation, low cost, reliable grid connected operation and good safety, namely, the two phase half wave reactance shunt excitation system, is proposed. Test results show that the new system has a larger voltage setting range than the original system, and it is economical in hydropower station transformation and can support reliable grid connected operation. It is recommended to use this system in the operation of self excited constant voltage synchronous generators of small hydropower stations in rural areas.