In this paper, a nanosecond pulse power supply is employed to excite the gas-liquid discharge in atmospheric air, and the discharge characteristics, plasma characteristics and the composition of activated water under different pulse parameters are studied. The results show that the discharge consists of three stages in one pulse period, among which the two discharges that occur during the pulse duration and the falling edge are stronger, and the discharge on the rising edge is weaker. When the pulse voltage increases, the discharge current, average power, luminous intensity and spectra intensity all gradually increase. When the frequency increases, the discharge current is almost unchanged, but the power increases significantly, the discharge luminous and spectra intensity also increase. The increase of the voltage rising edge time will weaken the discharge intensity, and the corresponding luminous intensity and spectra intensity will be weakened. The increase of the voltage falling edge enhances the discharge, and the luminous intensity and emission spectra intensity increase. When the pulse voltage, frequency and falling edge time increase, the concentration of H₂O₂, ${\rm{NO}}_2^ - $ and ${\rm{NO}}_3^ - $ gradually increases. The increase of the rising edge time results in the decrease of the three active species concentrations. These results are helpful to understand the mechanisms of gas-liquid discharge characteristics under different conditions, so as to control plasma and solution activity, which will promote further practical application of nanosecond pulse gas-liquid discharge.