Based on two-dimensional steady magentohydrodynamic (MHD) model, the influence of gap distance change on vacuum arc characters is simulated and analyzed. Firstly, vacuum arc with constant current and variational gap distance is studied. It could be known that, with the increase of gap distance, the magnitude of vacuum arc plasma parameters increases and the radial asymmetry of them aggravates. Secondly, vacuum arc with half-wave sinusoidal current and linearly increased gap distance from a time point after arc ignition is simulated. The half-wave current is discreted at a series of discrete moments and the gap distance values are also gotten at these moments, then simulations are done at these time points respectively. By comparison among these simulation results, it could be known that the magnitude of arc plasma parameters increases firstly then decreases and their radial asymmetry follows the same trend, but the transition occurs not at current peak but after it.
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