The invention relates to a trigger circuit of a water-cooling radiating light-control thyristor valve group of a voltage class more than 66 kV, which triggers a light-control thyristor by adopting a laser trigger signal. The trigger circuit comprises a photoelectric isolation circuit, a pulse circuit 1, a pulse circuit 2, a combiner circuit and a drive circuit, wherein a trigger pulse input signal passes through the photoelectric isolation circuit so that a light signal is converted into an electric signal and is isolated and amplified and also passes through the pulse circuit 1 and the pulse circuit 2 so that two pulse signals with different fixed widths and different amplitude values are output; and the signals are rectified and then delivered to the combiner circuit so as to form a strong trigger signal and then trigger the light-control thyristor through trigger fibers. The trigger circuit can meet the requirements of a high voltage class, and has good stability, high interference resistance and reliability and long service life.