Abstract: The combination of pulse transformer and sharpening switch is a relatively mature way to generate nanosecond pulse. In this way, a compact high voltage repetitive nanosecond pulse generator (HRNPG) based on Tesla transformer and spark switch is developed in this paper. The pulse generator mainly consists of a repetitive charging module, a Tesla transformer and a sharpening switch. Repetitive charging module is mainly implemented by temporal coordination of two thyristors, Tesla transformer is the core of the pulse generator and main booster module, sharpening switch is a three electrode self-breakdown type gas switch, which is used to sharpen the transformer secondary voltage into nanosecond pulse waveform. Each part of the HRNPG is presented and tested in detail. Applied to a 6 k resistor, the HRNPG prototype is capable of generating a pulse with 100 kV peak voltage and 30 ns rise time at the maximum repetition rate of 500 Hz.