A 50 kV compact automatic nanosecond pulse source was developed. The working principle of the pulse source, its structure design and the development of automatic control system are introduced. The typical electric field waveform of a pulse source connected to a guided wave antenna is given. The output voltage of the pulse source can be adjusted continuously by DC capacitor charging method, and the output pulse width can be adjusted by changing the storage capacitance. The pulse source can be used to generate electromagnetic environment and test the breakdown characteristics of insulating materials. The output of higher voltage can be realized by selecting and designing higher voltage storage capacitors and charging insulators.