The multiple X-line reconnection process, which was proposed by Lee and Fu [1985> for the dayside magnetopause, is simulated based on a two-dimensional incompressible MHD model. It is found that when the system length is much larger than the thickness of the current layer, magnetic flux tubes are repeatedly formed and convected out of the system. Impulsive magnetic reconnections associated with the formation of magnetic flux tubes are observed. In the case of the dayside magnetopause, magnetic flux tubes with a cross-section of ~1 R2E are found to be formed repeatedly every 5-10 minutes, consistent with satellite observations.