In the paper are given the results of developing a nanosecond SHF pulse shaper with laser ignition. The main attention is paid to increasing the output pulse amplitude stability. The SHF pulses with the duration of 5 ns and the amplitude instability <2% in the range of peak powers of 5-15 MW are obtained. The time spread of the SHF pulse shaping moment relative to laser pulses does not exceed 0.6 ns. The ignition of a SHF commutating discharge is carried out by ultraviolet radiation of a nitrogen laser at λ=337.1 nm. The working gas is a dry air or nitrogen at the pressure of 1·105-1.14·105 Pa