Based on the avalanche effect, a kind of kilo-volt nanosecond pulsers has been designed, by using microwave PCB (printed circuit board). Its trigger signal with tunable repetition rate is given by a digital circuit. The full width of the pulse is tunable between 400ps and 2ns. Its voltage ranges from 360 to 2600V. And the peak power reaches 135kW. The design of these pulsers is discussed in detail, including the circuit design, the component selection, and the important physical layout. A novel method, called deficit-charge method, and a comb PCB layout are brought forward, aiming at solving the special problems caused by the high-power butultra-narrow pulser. Being used in the impulse radar test system, the circuit performance is excellent and stable.