Abstract: A frontogenesis model is studied, which includes three kinds of stratification profiles and synoptic-scale potential temperature field with different amplitudes, as well as mesoscale potential temperature disturbances fields placed at different heights. The time changes of vertical motion field are shown. The results show that atmospheric stratification and mesoscale potential temperature disturbances play important roles in the formation of multiple band of vertical motion. The mesoscale disturbance which has considerable vertical extent and is located at lower-level has the most important influence, and may be a possible mechanism triggering the formation of multiple rainbands in the warm-sector ahead of the cold front if the stratification is suitable, and that located at upper-level is unimportant. The amplitude of synoptic-scale potential temperature field is of great importance to the speed of frontogenesis and vertical motion field, but the effect of mesoscale disturbance on the speed of fronto-genesis is very little.