Abstract: The paper aims to study the mechanisms of the influence of discharge parameters on the discharge processes of gas spark switches under the pulse voltages with rise time of tens of nanosecond. On the basis of the field emission assumption, we numerically simulated the formation and development processes of nanosecond pulsed discharge channels of the homogenous electric field nitrogen gap at atmospheric pressure using a three-dimensional particle-in-cell, Monte Carlo-collision model for different discharge parameters. The effects of discharge parameters on the morphology and structure of the electron avalanche and streamer are analyzed by adjusting the parameters such as pulse voltage rise time, initial electrons density, and field-enhancement factor. The simulation results indicate that the electron avalanche propagates towards the anode, while the streamer simultaneously develops towards both the anode and cathode. The streamer channel exhibits obvious branches. There are differences in the propagation speed and morphology and structure of streamer channel for different discharge parameters. For the same initial electron density, the discharge propagation speed decreases, and the bifurcations of streamer channel become more obvious with the increase of pulse voltage rise time. For the same pulse voltage rise time, initial electrons with higher density can promote the formation and development of streamer, and weaken the bifurcations of streamer channel. The pre-ionization effect can be realized with a higher field-enhancement factor to effectively promote the steady generation and propagation of streamer, while minimizing the bifurcation phenomenon of streamer channel to the maximum extent.