In this 3-D numerical simulation, the influence of ignition position on flame propagation speed along a line vortex was investigated. The ignition distance between the vortex center line and the ignition point was changed from 0 mm to 2 mm, and the vortex core diameter was set at 2 mm or 4 mm. As a result, at the optimal ignition distance of about 0.8 mm, the fastest startup of flame propagation occurred and the average flame propagation speed had a maximum value in both cases of the vortex core diameter of 2 mm and 4 mm. The relationship between such a phenomenon and the vortex bursting mechanism by the spiral vortex line (the vortex filament soliton) was discussed.